Topic 2 lecture note..

Cell adhesion: Roles in lymphocyte recirculation,
trafficking, and microenvironment-specific homing
A/Professor Geoff Krissansen Ext 86280
Cell to cell, and cell to matrix interactions are fundamental biological processes which
regulate cell motility, migration, localisation, differentiation, and proliferation in all
multicellular organisms. In this course we will define the families of cell adhesion
molecules which sit on the outside of cells enabling cells to communicate with one
another, and to respond to the immediate microenvironment. Brief descriptions of the
structures, functions, and expression of various cell adhesion molecules, including the
Integrins, Ig CAMs, Cadherins, Selectins, Mucins, and extracellular matrix molecules.
The "area code" molecules, in particular the chemokines, that direct leukocyte traffic, and
microenvironment-specific lymphocyte homing will be analysed.
Leukocyte integrins
I-domain
subunit
Ligand
*
Ca++
MIDAS
subunit
subunit
MIDAS
Ligand
subunit
-propeller
Ca++
Ca++
Ca++
-propeller
Ca++
Ca++
Ca++
MIDAS
EGF-like cysteine-rich repeats
EGF-like cysteine-rich repeats
Post-translational cleavage
Transmembrane
domain
Non-I-domain integrin
Transmembrane
domain
I-domain integrin
Inactive
Active
From Cell, 110, Takagi J, Petre BM, Walz T, Springer TA

L, M, X, D, and E integrins are major receptors of the immune system
A subgroup of 2 integrins
The four -subunits of this subgroup assemble with the integrin 2-subunit to generate
the integrins L2 (LFA-1, CD11a/CD18), M2 (Mac-1, Mo-1, CR3, CD11b/CD18),
X2 (p150,95, CR4, CD11c/CD18), and D2 (CD11d/CD18) (Springer, 1995). They
are restricted to leukocytes, where L2 is expressed by most leukocytes, and M2 and
X2 are on monocytes/macrophages, granulocytes, large granular lymphocytes, and a
subpopulation of immature B cells. X2 is also present on some activated T cells.
L2: L2 mediates the adhesion of leukocytes to the intercellular adhesion molecules
ICAM-1, ICAM-2, and ICAM-3, which are inducibly or constitutively expressed on
many cell types. It participates in leukocyte transendothelial migration, recirculation,
homing, and localization to inflammatory sites. L2 plays a key role in antigenpresentation,
T-cell costimulation, the cytotoxicity of T cells, delayed-type
hypersensitivity, and endotoxin shock.
Leukocytes from mice lacking L display defects in in vitro homotypic aggregation, in
proliferation in mixed lymphocyte reactions, and in response to mitogen. In vivo, host-vsgraft
reaction toward injected allogeneic cells is also reduced. Neutrophils and activated
T lymphocytes are unable to cross endothelial cell monolayers in response to a
chemokine gradient. The trafficking of lymphocytes to peripheral lymph nodes, and, to a
lesser degree, to mesenteric lymph nodes and acute inflammatory sites is impaired.
Mutant mice mounted normal cytotoxic T cell (CTL) responses against systemic LCMV
and VSV infections, and showed normal ex vivo CTL function. However, they did not
reject immunogenic tumors grafted into footpads, and did not demonstrate priming
response against tumor-specific antigen. Thus L deficiency causes a selective defect in
induction of peripheral immune responses, whereas responses to systemic infection are
normal.
M2 and X2: M2 interacts with an assortment of ligands including ICAM-1,
iC3b, fibrinogen, serum factor X, and heparin, and may bind denatured proteins,
deoxyoligonucleotides, elastase, high molecular weight kininogen, and carbohydrate -
glucan structures. It interacts with the 3 rd Ig domain of ICAM-1, whereas L2 interacts
with the 1 st Ig domain. When L2 and M2 are expressed at similar levels, the L2
/ICAM-1 interaction dominates over the M2/ICAM-1 interaction.X2 binds to iC3b,
fibrinogen, and ICAM-1. M2 and X2 mediate myeloid cell adhesion to
endothelium, transmigration, chemotaxis, phagocytosis of opsonized particles, and
respiratory burst. M2-deficient mice have significant reductions in the numbers of
mast cells resident in the peritoneal cavity, peritoneal wall, and dorsal skin. Such mice
exhibit significantly increased mortality to acute septic peritonitis, where host resistance
depends on both mast cells and complement.
D2: D2 binds preferentially to ICAM-3. The D subunit is more closely related to
M and X than to L. D2 is expressed at moderate levels on myelomonocytic cell
lines, and subsets of peripheral blood leukocytes. It is strongly expressed on tissue-

compartmentalized cells such as macrophage foam cells found in aortic fatty streaks that
may develop into atherosclerotic lesions. It is also expressed on eosinophils and binds
VCAM-1, suggesting it may play a role in eosinophil adhesion to VCAM-1 in states of
chronic inflammation. The ICAMs are expressed on dendritic cells, and other antigen
presenting cells, and deliver costimulatory signals via 2 integrins to trigger lymphocyte
proliferation.
E associates with the 7-subunit
The E subunit associates with the 7-subunit, forming the E7 (HML-1, human;
M290, mouse; CD103/7) activation antigen which recognizes epithelial E-cadherin. It
has been proposed to retain iIEL as an immune barrier against intestinal pathogens. E7
is expressed on only 2% of circulating blood lymphocytes and is upregulated by TGF-
a cytokine which may imprint migratory gut-seeking lymphocytes to become resident
as iIELs. The E7 binding site within E-cadherin is distinct from the site used by E-
cadherin for homophilic binding. 7 -/- mice are viable, but have impaired gut-associated
lymphoid tissue including reduced numbers of intraepithelial lymphocytes, and
lymphocytes in the Peyer’s patches, mesenteric lymph nodes, and lamina propria.
Mucosal T lymphocyte numbers are selectively reduced in E -/- mice, including intestinal
and vaginal IEL, and lamina propria lymphocytes. In contrast, peribronchial,
intrapulmonary, Peyer's patch, and splenic T lymphocyte numbers were not reduced,
suggesting that E7 is important for generating or maintaining the gut and vaginal T
lymphocytes located diffusely within the epithelium or lamina propria but not for
generating the gut-associated organized lymphoid tissues.
4 integrins are major immunoreceptors that recognize Ig-family counterreceptors
4 integrins are predominantly expressed on leukocytes, and play key roles in immune
responses. The 4 subunit assembles with the 1 and 7 subunits, producing the integrins
41 (VLA-4) and 47 (LPAM-1), respectively. These two integrins share the ligands
VCAM-1, MAdCAM-1, and FN; where 41 preferentially binds VCAM-1 on activated
endothelium and 47 preferentially binds MAdCAM-1 expressed on high endothelial
venules (HEV) at sites of chronic inflammation. 41 binds to Ig domains 1 and 4 of
VCAM-1, whereas 47 binds to Ig domain 1 of MAdCAM-1 with assistance from
domain 2. Both 4-integrins are expressed on the microvillus tips of lymphocytes, unlike
L2 which is restricted to the planar surface; and can mediate lymphocyte tethering and
rolling under shear flow. 4-integrins also mediate the initial attachment of eosinophils.
41 is more widely expressed, being found outside the leukocyte lineages on myoblasts,
endothelial and melanoma cells. The interaction of 41 with VCAM-1 may facilitate
transendothelial chemotaxis by supporting the lateral migration of attached monocytes
along the endothelium.
Other functions for 41, some of which may be shared with 47, include facilitating
the attachment and emigration of leukocytes across the blood vessel wall, the adhesion
and prevention of apoptosis of B cells in germinal centres, and the adhesion of lymphoid

progenitors to bone marrow stroma. Production of T cells in the adult is 4-dependent,
and precursors for both T and B cells require 4-integrins for normal development within
the bone marrow. Antibodies against 47 or MAdCAM-1 block the binding of
mesenteric lymph node lymphocytes to Peyer’s patch (PP) HEV in vitro, and the homing
of lymphocytes to the gut and lamina propria in vivo. Hence 47 is critical for the
homing of lymphocytes to the gut, and mucosal sites which are normally chronically
inflamed. 4 integrins have an ability to compensate for the lack of LFA-1 in facilitating
the migration of lymphocytes to peripheral lymph nodes in LFA-1-deficient mice.41
also participates in lymphocyte recirculation through bone marrow.
4 integrins, and their ligands are highly expressed on pathogenic leukocytes, and
diseased tissues at sites of chronic inflammation, and hence are major targets for the
treatment of many of the major chronic inflammatory disease. The 4-integrin ligands
VCAM-1 and MAdCAM-1 are expressed on follicular dendritic cells, and may deliver
signals via 4 integrins during antigen presentation, leading to costimulation of T cell
proliferation.
Ig CAMS
LFA-1
ICAM-3
CD50
Leukocytes activated resting activated HEV
endothelium endothelium endothelium
activated leuk resting lymph/mono macrophage
ICAM-1 (CD54)
Intercellular adhesion molecule-1(ICAM-1) is a single chain 80-114 kDa protein with
five Ig-like domains, a single transmembrane region, and a short cytoplasmic domain. It
can bind to LFA-1, Mac-1, fibrinogen, hyaluronan, and CD43. Resting leukocytes
express little or no detectable ICAM-1, but expression is induced following activation.
Resting endothelial cells have low levels of ICAM-1, and activation with inflammatory

cytokines such as IL-1, IFN-, and TNF-results in increased expression on endothelial
cells in addition to induction on epithelial cells. It is expressed on dendritic cells, where
the interaction of ICAM-1 with LFA-1 is thought to be involved in the initial binding of
T cells to antigen presenting cells.
ICAM-2 (CD102)
ICAM-2 (55-65 kDa) has two Ig-like domains. Resting lymphocytes and monocytes, but
not neutrophils, express low levels of cell surface ICAM-2. Immunohistochemical
analysis indicates high expression of ICAM-2 on endothelium and on follicular dendritic
cells in lymph node germinal centers. ICAM-2 is not upregulated on leukocytes or
cultured endothelium following stimulation with inflammatory mediators. Ligands
recognized by ICAM-2 include LFA-1 and Mac-1. The precise role of ICAM-2 is not
understood, but it is thought to be important in recirculation of leukocytes through
uninflamed tissue endothelium.
ICAM-3 (CD50)
ICAM-3 is a 120-160 kDa molecule and, like ICAM-1, it contains five Ig domains. It is
constitutively expressed at high levels on leukocytes, but, in contrast to ICAM-1 and
ICAM-2, it is not found on most endothelial cells. ICAM-3 binds to LFA-1, but not Mac-
1. It is expressed on dendritic cells, where the interaction of ICAM-3 with LFA-1 is
thought to be involved in the initial binding of T cells to antigen presenting cells.
VCAM-1 (CD106)
Vascular cell adhesion molecule (VCAM-1) (110 kDa) has seven Ig-like domains.
Expression is induced on endothelial cells by inflammatory mediators such as IL-1 and
TNF-. VCAM-1 is also expressed on some macrophages, dendritic cells, bone marrow
stromal cells, synovial cells in inflamed joints, and muscle cells. VCAM-1 is recognized
by the integrins 41 (VLA-4) and 47 and supports the extravasation of leukocytes,
particularly at sites of inflammation. In addition, VCAM-1 can participate in adhesion
outside the vasculature, including binding of lymphocytes to dendritic cells and bone
marrow stromal cells.
PECAM-1 (CD31)
Among the molecules known to (secondarily) activate the integrins are the chemokines
and platelet-endothelial cell adhesion molecule-1 (PECAM-1, CD31 or endoCAM). Once
a leukocyte binds to endothelium via an integrin-immunoglobulin (Ig) superfamily (IgSF)
interaction, it "searches" for junctions between endothelial cells, first squeezing between
these potential discontinuities, and then penetrating the underlying basement membrane
to reach the tissues. Human CD31 is a 130 kDa, type I (extracellular N-terminus)
transmembrane glycoprotein that possesses six Ig-domains. Most, if not all, activities
associated with CD31 can be attributed to homophilic CD31-CD31 interactions. Among
these are leukocyte extravasation, bone marrow hematopoiesis, and vascular
development. During the events surrounding leukocyte extravasation, CD31 seems to be
most important during the later stages. It facilitates the binding of various leukocyteassociated
integrins to ICAM/VCAM IgSF members and assist peripheral blood

leukocytes in their transit across endothelial barriers. On T cells, CD31 ligation will
upregulate the adhesive function of both 1 and 2 integrins.
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E-Cadherin
Epithelial cadherin is a 120-kDa cell surface glycoprotein that, when complexed with
catenins, mediates Ca2+-dependent cell-cell adhesion. E-cadherin forms the key
functional component of adherens junctions of all epithelial cells. It plays a major part in
the establishment and maintenance of intercellular adhesion, cell polarity and tissue
architecture. Loss of cadherin mediated adhesion seemed to be an important contributory
factor in tumour pathogenesis. In terms of immunity, it plays a critical role in localizing
intraepithelial lymphocytes to epithelial regions by binding to E7. This is particularly
important for gut mucosal immunity.
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Selectins
Selectins are a family of transmembrane molecules, expressed on the surface of
leukocytes and activated endothelial cells. Selectins contain an N-terminal extracellular
domain with structural homology to calcium-dependent lectins, followed by a domain
homologous to epidermal growth factor, and two to nine consensus repeats (CR) similiar
to sequences found in complement regulatory proteins. Each of these adhesion receptors
is inserted via a hydrophobic transmembrane domain and possesses a short cytoplasmic
tail. The initial attachment of leukocytes, during inflammation, from the blood stream is
afforded by the selectin family, and causes a slow downstream movement of leukocytes
along the endothelium via transient, reversible, adhesive interactions called leukocyte
rolling. Each of the three selectins can mediate leukocyte rolling given the appropriate
conditions.
L-selectin
P-selectin
E-selectin

L-Selectin
The smallest of the vascular selectins, a 74-100 kDa molecule, is constitutively expressed
at the tips of microfolds on granulocytes, monocytes, and a vast array of circulating
lymphocytes. L-selectin is important for lymphocyte homing and adhesion to high
endothelial cells of post capillary venules of peripheral lymph nodes. Moreover, this
adhesion molecule contributes greatly to the capture of leukocytes during the early phases
of the adhesion cascade. Following capture, L-selectin is shed from the leukocyte surface
after chemoattractant stimulation. L-selectin interacts with three known counter receptors
or ligands, MAdCAM-1, GlyCAM-1, and CD34.
In L-selectin deficient mice, or following anti-L-selectin mAb treatment, trauma-induced
leukocyte rolling in mesentary or cremaster muscle venules is normal initially, but
declines over time. This indicates that trauma-induced rolling in these mice is P-selectin
dependent with a velocity highly comparable to that observed in wild-type mice. L-
selectin is critical in mediating rolling after surgical trauma and is necessary for
neutrophil recruitment after inflammation. Nevertheless, basal neutrophil trafficking
appears to remain unaffected by absence of L-selectin since peripheral leukocyte and
neutrophil counts in these mice were normal.
Leukocyte rolling is P-selectin dependent in TNF--treated mice deficient in L-selectin,
The lack of L-selectin in these mice reduces the efficiency of E-selectin-mediated rolling
as shown by the sensitivity of rolling to P-selectin antibodies. These experiments
consistently show that L- and P-selectin mediate leukocyte rolling, however, L-selectin
alone cannot assume this task at normal velocities in vivo. L- and P- selectin cooperate in
such a way that in the absence of P-selectin, L-selectin must initiate leukocyte
interactions to allow slow rolling on E-selectin (but see below). In addition, L- or P-
selectin must be present to mediate capture before the commencement of leukocyte
rolling. Without the presence of either L- or P-selectin, rolling cannot occur.
Levels of L-selectin are higher on lymph node-homing T cells, which may facilitate T
cell accumulation at this site by enhancing binding to locally expressed ligands such as
PNAd.
P-selectin
P-selectin is the largest of the known selectins at 140 kDa. It contains nine consensus
repeats (CR), and is expressed in -granules of activated platelets and granules of
endothelial cells. Within minutes of stimulation of the endothelial cells by inflammatory
mediators such as histamine, leukotrienes, thrombin, or phorbol esters, P-selectin is
surface-expressed. The primary ligand for P-selectin is PSGL-1 (P-selectin glycoprotein
ligand-1) which is constitutively found on all leukocytes, and rapidly released from the
cell-surface following leukocyte activation. The transient interactions between P-selectin
and PSGL-1 allow leukocytes to roll along the venular endothelium. Accordingly, P-
selectin is largely responsible for the rolling phase of the leukocyte adhesion cascade. P-
selectin can also mediate capture when L-selectin is not present.

In mice deficient for P-selectin, trauma-induced rolling is absent immediately, but returns
after 1-2 hours. In this case, the delayed rolling is L-selectin dependent, but the
leukocytes roll much faster than in wild-type mice, suggesting that L-selectin cannot
independently support rolling at typical in vivo velocities. On the other hand, in L-
selectin deficient mice, P-selectin mediates most trauma-induced leukocyte rolling.
Normal leukocyte rolling is seen for approximately 90 minutes, showing that P-selectin
has the ability to capture leukocytes from the bloodstream and start them rolling along the
endothelium even without the presence of L-selectin.
In TNF--stimulated venules, P-selectin and E-selectin tend to have overlapping
functions. In mice deficient for P-selectin, it is necessary to block E-selectin function to
significantly reduce rolling, and in E-selectin knockouts, an antibody against P-selectin
must be introduced to reduce rolling. Correspondingly, no leukocyte rolling is observed
in E-selectin/P-selectin double deficient mice treated with TNF-. Although P- and E-
selectin seem to have redundant functions, observations of rolling flux fraction and
rolling velocity indicate that P-selectin is responsible for early rolling while E-selectin
allows slow rolling and more adhesion.
E-selectin
E-selectin is expressed on inflamed endothelial cells in response to treatment with
inflammatory cytokines. Intravital microscopic experiments have shown that its function
in mediating leukocyte rolling is largely redundant with that of P-selectin. Consequently,
E-selectin deficient mice have only a subtle defect in leukocyte rolling as shown by much
faster rolling velocities in these mice. In addition to mediating leukocyte rolling, E-
selectin participates in the conversion of rolling to firm adhesion. E-selectin-deficient
mice have a reduced number of firmly adherent leukocytes in response to local
chemoattractant or cytokine stimulation. This defect may be related to the more rapid
rolling velocities in the absence of E-selectin. E-selectin is expressed in skin microvessels
under baseline conditions, and there is some evidence that E-selectin is of particular
importance in skin inflammation, because it supports the recruitment of skin-specific T
lymphocytes.The ligands for E-selectin that are responsible for the rolling interaction are
unknown. Two candidate ligands, PSGL-1, and E-selectin ligand-1 (ESL-1) have not
been shown to be required for E-selectin mediated leukocyte rolling under any condition.
**************************************************************************************

Mucins
Selectin ligands are mucins. Mucins are serine and threonine-rich, providing sites and a
scaffold for O-link glycosylation.
PSGL-1
P-selectin glycoprotein ligand-1 is a 240 kDa homodimer consisting of two 120kDa
polypeptide chains. PSGL-1 is constitutively expressed on all leukocytes. PSGL-1 is
primarily found on the tips of the microvilli. PSGL-1 can bind to P-selectin on the
endothelium when decorated with appropriate sugars. The structure of functional PSGL-1
includes the sialyl-Lewis x component. The PSGL-1 gene encodes a transmembrane
polypeptide rich in proline, serine and threonine residues typical of mucin-type
glycoproteins. The O-linked glycans displayed by PSGL-1 must undergo two specific
post-translational modifications in order for it to function as a counter-receptor for P-
selectin: (1,3) fucosylation and (2,3) sialylation. PSGL-1 can also bind L-selectin and
E-selectin. CLA the skin homing receptor is a specially modified form of PSGL-1 (see
later).
CD34
CD34 is a transmembrane glycoprotein constitutively expressed on endothelial cells and
on hematopoietic stem cells. This highly O-glycosylated molecule, containing serine and
threonine-rich mucin like domains, binds to L-selectin. Studies have suggested that CD34
is important in tethering lymphocytes. Mice deficient in CD34 exhibited no detectable

abnormalities in postsurgical leukocyte rolling in cremaster venules. Antibodies blocking
L-selectin function reduced rolling in CD34 deficient mice suggesting that CD34 lacks
major significance as a ligand for L-selectin.
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Chemoattractants
Extracellular matrix
In a lot of the connective tissues, the extracellular matrix molecules are secreted by cells
called fibroblasts. These molecules assemble into the extracellular matrix once they are
secreted. The extracellular matrix is made up of two classes of macromolecules. The first
class is called glycosaminoglycans, which are polysaccharide chains. Members of this
class are usually found to be covalently linked to protein in the form of proteoglycans.
The second class is made up by fibrous proteins. There are two functional types of
fibrous proteins: the ones that are mainly structural, like collagen and elastin for example,
and the ones that are mainly adhesive, like fibronectin and laminin for example. The
members of the glycosaminoglycans form a highly hydrated, gel-like substance, in which
the members of the fibrous proteins are embedded. Collagen fibers strengthen and help to
organize the matrix, while elastin fibres give it resiliance. The adhesive proteins help
cells to attach to the extracellular matrix. Fibronectin for example promotes the
attachment of fibroblasts and other cells to the matrix in connective tissues via the
extracellular parts of some members of the integrin family, while laminin promotes the
attachment of epithelial cells to the basal lamina, again via the extracellular domains of
some members of integrins.
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Multistep process of leukocyte extravasation
The stimulus for endothelial activation in vivo is probably local production of cytokines
and other inflammatory mediators released on tissue injury.
Capture
The process known as capture or tethering represents the first contact of a leukocyte with
the activated endothelium. Capture occurs after margination, which allows leukocytes to
move in a position close to the endothelium, away from the central blood stream. During
the inflammatory response, endothelial activation is required to initiate capture.
P-selectin on endothelial cells, is the primary adhesion molecule for capture and the
initiation of rolling. The main leukocyte ligand for P-selectin is PSGL-1. In addition,
many in vivo studies suggest that L-selectin exhibits an important role in capture as well.
Antibodies blocking L-selectin function inhibit rolling in many models in which rolling is
P-selectin dependent.
EFigure 10. Expression of ICAM-3 (CD50)
E-cadherin.10)

Rolling
Once leukocytes are captured, they may transiently adhere to the venular endothelium
and begin to roll. Rolling occurs at or below the velocity of freely flowing cells. The
velocity separating rolling from freely flowing cells is called critical velocity or
hydrodynamic velocity. P-selectin is the most important selectin involved in rolling. P-
selectin can support both capture and rolling in the absence of L-selectin. Although P-
selectin was initially identified on activated platelets, it is also found in Weibel-
Palade
The multistep process of leukocyte extravasation
Margination
Luster et al. Nature Immunology 6: 1182-1190, 2005
bodies of human endothelial cells. Upon stimulation by trauma, P-selectin is rapidly
surface-expressed on the venular endothelium, and it makes the endothelium "sticky" to
leukocytes. PSGL-1 (P-Selectin Glycoprotein Ligand-1) is constitutively expressed on all
lymphocytes, monocytes, eosinophils, and neutrophils. PSGL-1 on neutrophils,
eosinophils, and monocytes has a glycosylation pattern allowing it to bind to endothelial
P-selectin. As a result, the leukocyte rolls along the endothelium. During rolling, bonds
are formed at the leading edge of the rolling cell and broken at the trailing edge.
Leukocyte integrins initially remain in their resting state, and endothelial IgCAMs remain
at control levels.
The critical role of P-selectin in the rolling phase of the adhesion cascade is supported in
experiments done on gene-targeted mice. In mice lacking P-selectin, leukocytes do not
roll on the venular endothelium after surgical trauma. Also, when compared with wildtype
mice, the number of circulating granulocytes is greater in P-selectin deficient mice.
This suggests that P-selectin is necessary to remove the leukocytes from the bloodstream

so they may stick and roll along the venular endothelium. In vitro, isolated human
granulocytes have been shown to roll on purified P-selectin using flow chamber systems.
L-selectin and E-selectin also take part in the rolling process. When P-selectin is absent,
trauma-induced rolling becomes L-selectin dependent, but the average leukocyte rolling
velocity is three to five times faster in this case. This suggests that L-selectin is much less
efficient than P-selectin in mediating the rolling process. However, L-selectin is
necessary for the normal inflammatory response in capturing leukocytes and initiating
rolling. An apparent redundancy exists between P- and E-selectin in mediating leukocyte
rolling on cytokine-activated endothelium. E-selectin is thought to be responsible for
slow rolling interactions, and possibly the initiation of firm adhesion.
Slow rolling
After induction of inflammation by injection of a pro-inflammatory cytokine like TNF-,
leukocyte rolling velocity drops dramatically to an average between 5 and 10 µm/s. This
rolling requires the expression of E-selectin on endothelial cells and CD18 integrins on
the rolling leukocytes, and has been termed "slow rolling" to distinguish it from the much
faster rolling without cytokine stimulation. Slow rolling is not based on a unique property
of E-selectin, but the expression of E-selectin and/or its ligands appears to be sufficiently
high in vivo to support slow rolling. The contact time during which the leukocyte is in
close proximity with the endothelium, appears to be a key parameter in determining the
success of the recruitment process as reflected in firm adhesion. The important role of
leukocyte transit time appears to be related to chemokines that are presented on the
endothelial surface and are likely to be accessible to the leukocyte as long as it rolls. This
is supported by tracking studies, in which individual rolling leukocytes were found to
slow down systematically before becoming firmly adherent. Rolling leukocytes are likely
to be activated by surface-bound chemoattractants and through adhesion molecule-based
signaling. It is also possible that the velocity of rolling may have an effect independent of
transit time, because secondary binding events (e.g., 2 integrin-mediated) may not be
able to form unless the leukocyte spends a certain amount of time in a position favorable
for bond formation. Although slow rolling makes leukocyte recruitment much more
efficient, it is not strictly required, because high concentrations of chemoattractants can
also arrest fast-rolling leukocytes. Chemokines activate integrins resulting in firm
adhesion of leukocytes to the vascular wall.
Firm adhesion
It is thought that most if not all leukocytes adhere only after having rolled. Several
studies suggest that direct adhesion (from the free-flowing leukocyte pool) is extremely
rare. E-selectin participates in the conversion of rolling to firm adhesion. E-selectin
deficient mice have a reduced number of firmly adherent leukocytes in response to local
chemoattractant or cytokine stimulation.
Interfering with CD18 integrin function is one of the most efficient ways to curb
leukocyte recruitment in many forms of experimental inflammation. Although the
response to exogenous chemoattractant is drastically reduced when CD18 is absent or not
functional, cytokine treatment still yields a robust inflammatory response in gene-

targeted mice lacking CD18. This suggests that CD18 integrins participate in leukocyte
arrest, but are not always required. Neutrophils express small amounts of other integrins,
including 41 integrin, which may be important in these alternative pathways.
However, CD18 deficient mice have severe inflammatory defects including skin
ulcerations, elevated neutrophil counts and immunoglobulin levels, increased
susceptibility to streptococcus pneumoniae, and a severe defect in leukocyte adhesion and
T-cell activation, a defect in leukocyte recruitment to peritonitis, and a lack of neutrophil
recruitment to the skin. Patients lacking CD18 expression suffer from leukocyte adhesion
deficiency type 1 (LAD-1). When CD18 is totally absent, LAD-1 is a very severe disease,
which can lead to early lethality.
Leukocytes rolling in resting inflamed venules require ICAM-1 to stop in response to a
chemoattractant. However, ICAM-1 is no longer required after activation with
inflammatory cytokines. Monocytes, eosinophils, and many lymphocytes express 41
integrin (VLA-4), and mouse and rat neutrophils also express small amounts. When other
adhesion molecules are unavailable, 41 integrin can mediate both leukocyte rolling,
and firm adhesion. 41 integrin binds to endothelial VCAM-1, and alternatively spliced
fibronectin. Intravital microscopic evidence available to-date suggests that most 4-
dependent binding is through VCAM-1, because antibodies to VCAM-1 applied in the
microcirculation and in atherosclerotic arteries block leukocyte rolling and adhesion to a
similar extent as 4 antibodies.
Transmigration
Leukocytes migrate across resting endothelium if an exogenous chemoattractant is
present. This has been termed "leukocyte driven" or chemotactic transmigration. The
pathophysiological hallmark of established inflammatory transmigration is endothelial
activation, an event requiring transcription and protein synthesis. As a result adhesion
molecules are upregulated, inflammatory mediators are produced, and the endothelium
secretes chemoattractants, all of which contribute to transmigration. Endothelial
chemokines are critical for transmigration. Chemokines have heparin binding sites which
allow them to bind proteoglycans on the vascular endothelium, positioning them for
activating integrins. A number of adhesion molecules have been implicated in
transmigration, although the level of confidence in their actual involvement varies,
including PECAM-1, ICAM-1, VE-cadherin, CD11a/CD18 (LFA-1), IAP (CD47) and
VLA-4 (41 integrin). The cells upon activation by integrins release heparin binding
protein (HBP) which causes increases in microvascular permeability which allows for
leukocyte transmigration.
In vivo, ICAM-1 knock-out mice show significantly impaired neutrophil migration into
inflamed peritoneum, and ICAM-1 antibodies reduce acute and chronic inflammation in a
number of animal models. ICAM-1 antibodies reduce cytokine-activated transmigration
of neutrophils in vitro, by over 85%. ICAM-1 is also important in chemotactic
transmigration. Antibodies inhibit neutrophil chemotactic transmigration by ~55%.
PECAM-1 (Platelet-Endothelial Cell Adhesion Molecule-1, CD31) is critical in passage
through the junction in cytokine-activated transmigration. Anti-PECAM-1 antibodies
reduce monocyte transmigration through resting endothelium, and both monocyte and

neutrophil transmigration through cytokine activated endothelium by 70-90%. Binding of
leukocytes to endothelium is not affected. Although V3 integrin can be a ligand for
PECAM-1, and monocytes lacking 3-integrin transmigrate poorly, this appears to be
due to modulation of CD11a/CD18 rather than by an interaction with PECAM-1. In
contrast to cytokine-activated transmigration, PECAM-1 seems to have little role in
chemotactic transmigration. PECAM-1 antibodies do not decrease chemotactic
transmigration in vivo, nor do they decrease transmigration triggered by thrombin. In
addition, there is often a significant residual transmigration (~10-30%) after PECAM-1
inhibition which suggests that other mechanisms may operate in passage through the
junction in cytokine-activated transmigration. These observations suggest that the
mechanisms operating in cytokine-activated and chemotactic transmigration overlap to
only a small degree. Neutrophils and monocytes from CD11a knock out mice do not
require PECAM-1 for transmigration, suggesting that CD11a and PECAM-1 somehow
operate in a similar pathway of migration. However, PECAM-1 knockout mice show no
clear evidence of a transmigration defect.
The involvement of VLA-4 in transmigration in vitro is variable. It is likely this reflects
redundancy with 2-integrins, as well as the degree of VCAM-1 expression on
endothelium, which in turn reflects the state of endothelial activation. It appears
unimportant in neutrophil transmigration in vitro, and in transmigration of activated T-
cells. Resting T-cell and NK cell cytokine-activated transmigration are reduced by 40%
and 30% respectively (Oppenheimer Marks et al 1991; Bianchi et al 1993). As firm
adhesion is reduced to a similar extent it is unclear whether this is a specific effect on
passage across the endothelium.
**************************************************************************************
Ectoenzymes in the control of leukocyte traffic
Ectoenzymes are membrane proteins that have their active site outside the cell. They
include proteases, nucleotidases, and oxidases, which can regulate leukocyte
transmigration.
Nucleotidases:
ATP is proinfammatory: ATP binds purinergic receptors of the P2X and P2Y
families, and induces proliferation by inducing cytokine expression, and activating
dendritic cells.
Adenosine is anti-infammatory: Adenosine inhibits neutrophil adhesion to the
microvascular endothelium by activating the adenosine receptors A 2A R abd A 2B R on
neutrophils. Adenosine prevents leukocyte activation- it inhibits L-selectin shedding and
expression of CD18 integrins by leukocytes, and down-regulates VCAM-1 and cytokine
expression by endothelial cells.
CD73

CD73 is a glycosylphosphatidylinositol (GPI)-linked cell surface molecule expressed by
vascular endothelial cells and up to 15% of lymphocytes (but not by granulocytes and
monocytes). It catalyses the dephosphorylation of AMP to adenosine, indicating it has
anti-inflammatory properties. CD73 is increased in expression at sites of inflammation by
IFN. Mice deficient in CD73 show increased leukocyte attachment to the endothelium,
and leukocyte migration.
CD39
CD39 converts extracellular ATP to AMP, suggesting it has anti-inflammatory
properties. It is expressed by many different types of leukocytes, and by vascular
endothelial cells. Mice deficient in CD39 display exacerbated skin inflammation by
irritants.
Both ATP-generating and ATP-consuming pathways coexist on the surfaces of
leukocytes and endothelial cells. Their balance regulates the level of ATP and adenosine,
and hence influence the local inflammatory environment.
ATP is dephosphorylated to AMP by CD39 on resting endothelium, and AMP is
dephosphorylated to adenosine by CD73. This is expected to create an anti-inflammatory
setting. The activity of CD73 is inhibited when lymphocytes attach to the endothelium,
and hence less adenosine is produced, which leads to increased leukocyte migration.
ADP-ribosyltransferases:
ADP-ribosyltransferases such as ART2 transfer the ADP-ribose moiety from NAD(P) to
an acceptor. The ADP-ribose moiety can covalently modify and inactivate several surface
proteins including L2. The homing of NAD(P)-treated T cells to lymph nodes and gut

lymphoid organs is inhibited, and injection of NAD(P) into mice markedly decreases T
cell homing. Note: 41 is not ADP-ribosylated, and B cells don’t express ART2, hence
their homing is not affected.
Ectopeptidases regulate chemokines
CD26 is an ectoenzyme that cleaves N-terminal dipeptides containing either proline or
alanine residues from polypeptides. CD26 is expressed de novo on activated T and B
cells, NK cells, and endothelial cells. Numerous bioactive peptides are cleaved by CD26,
including chemokines. Cleavage of chemokines by CD26 reduces their ability to bind and
activate chemokine receptors, whereas their ability to serve as chemoattracts can be
enhanced (eg CCL5). Rodents that are deficient in CD26 have increased infiltration of
leukocytes into the lung and joints in models of asthma and arthritis, suggesting that
CD26 plays a role in inhibiting inflammation.
Sheddases
CD156b is a sheddase that cleaves L-selectin from the surface of thymocytes. Other
sheddases are also involved. L-selectin is shed from lymphocytes to prevent re-entry of
activated T cells to secondary lymphoid organs.
Ectoenzymes in the control of leukocyte traffic
The nucleotidases CD39 and CD73 regulate the balance of ATP and adenosine, and the
activation of leukocyte integrins and vascular cell adhesion molecules. CD26
proteolytically modifies the activities of chemokines, whereas sheddases cleave leukocyte
cell adhesion molecules such as L-selectin. ADP ribosyltransferases such as ART2
modify and inactivate adhesion molecules.

Poorly characterized
**************************************************************************************
Trafficking of leukocytes to specific organs and tissues, and
microenvironment-specific homing
Tissue-restricted recirculation of memory and effector lymphocytes may serve to 1)
increase the efficiency of regional immune responses, and 2) allow functional immune
specialization of particular tissues. Differences in chemokine receptor, integrin, or
selectin expression plays a major role in selective leukocyte recruitment to different
tissues or organs, and positional localization with an organ. Chemokines play a major
role as they serve as attractants for inflammatory leukocytes, control leukocyte/integrin
activation, and control microenvironmental segregation within lymphoid organs. Table 1
shows examples of key molecules that control recruitment. Different chemokine
receptors are expressed depending on whether the T cell is naïve, or a memory cell, and
whether it is a Th1 or Th2 cell.
Table 1
Receptors on leukocytes that contribute to selective cell
recruitment
Leukocyte surface structure Ligands Pattern of leukocyte expression
Adhesion molecules

L-selectin PNAd, others All leukocytes, but naive T cells > memory T cells
PSGL-1 P-selectin All leukocytes, but eosinophils > neutrophils
CLA E-selectin Skin-homing memory T cells
Sialyl-dimeric Lex E-selectin All leukocytes, but neutrophils > eosinophils
41 integrin VCAM-1, others All leukocytes except neutrophils
47 integrin MAdCAM-1, others All leukocytes except neutrophils
E7 integrin E-cadherin Intraepithelial lymphocytes
Chemokine receptors
CCR3 Eotaxin 1-3, others Eosinophils, basophils, mast cells; some TH2 cells
CCR4 TARC, MDC Skin-homing memory T cells
CCR5 MIP-1 TH1 cells
CCR6 MIP-3 Memory T cells
CCR7 SLC (CCL21), Naive B and T cells
MIP-3 (CCL19)
CCR8 I-309 TH2 cells
CCR9 TECK Gut-homing memory T cells
CCR10 CTACK Skin-homing memory T cells
CXCR3 Mig, IP-10, I-TAC TH1 cells
CXCR5 BLC (CXCL13) Naive B cells
PNAd, Peripheral lymph node addressin; PSGL-1, P-selectin glycoprotein ligand-1; CLA, cutaneous
lymphocyte antigen; Lex, Lewis X; VCAM-1, vascular cell adhesion molecule-1; MAdCAM-1, mucosal
addressin adhesion molecule-1; TARC, thymus- and activation-related chemokine; MDC, macrophagederived
chemokine; MIP, macrophage inflammatory protein; SLC, secondary lymphoid tissue chemokine;
TECK, thymus-expressed chemokine.

Guidance of neutrophils to sites of sterile inflammation
A multistep cascade of molecular events guides the recruitment of neutrophils to sites of
sterile injury ie tissue injury in the absence of infection. Neutrophils contribute to the
clearance of debris from necrotic sites. They have an arsenal of destructive molecules
hence collateral tissue destruction needs to be avoided. Steps:
1. ATP released from necrotic cells at the wound site activates the NLRP3
inflammasome via the P2X7 receptor in inflammatory cells (macrophages)
resulting in release of IL-1.
2. IL-1 upregulates ICAM-1 on the vascular endothelium, leading to M2
integrin-mediated adhesion of neutrophils to microvascular endothelia near the
wound site within 30-60 minutes of injury.
3. The chemokine MIP-2 (CXCL2) released at the wound site forms a
chemoattractant gradient that surrounds but not does completely reach the injured
area. It is maximal at 100-150 m from the injury border.
4. Neutrophils migrate via an intravascular route to the site of injury.
5. MIP-2 attacts neutrophils up to the injury border (but what attracts neutrophils
into the necrotic lesion?).
6. Necrotic cells release mitochondria-derived formylated peptides, which over-ride
MIP-2 and guide neutrophils directly into the injury site via formyl peptide
receptor 1 signalling. This focuses the innate immune response on sites of damage
rather than healthy tissue.
Did this pathway evolve to limit collateral damage by allowing neutrophils to remain
intravascular during migration to the wound via healthy tissue? The pathway has been
established in liver, but also applies to skin.
Figure MIP-2 expression (red)
and PECAM-1+ endothelium
(blue) were visualized 2.5 hours
after injury.

Homing of lymphocytes to lymph nodes
Naïve T cells: Naïve T cells interact with high endothelial venules in lymph nodes via
L-selectin binding to PNAd, and LFA-1 binding to ICAM-1. These interactions are
stimulated by the chemokine SLC (displayed by HEV), which interacts with CCR7 on the
T cell. The positional localization of naïve T cells within the lymph node is controlled by
the production of MIP-3 within the T cell zone. Thus, the development of lymph nodes
is markedly reduced in L-selectin-deficient mice, such that there are few B and T cells.
The plt (“paucity of lymph node T cells”) mutant mouse deficient in SLC has lymph
nodes and Peyer’s patches that are deficient in T cells, but not B cells. B cells are not
dependent on SLC for entry through HEV. Normal T cells infused into these mice fail to
accumulate in lymph nodes. Injection of SLC into mice leads to uptake and display of
SLC on HEV of lymph nodes, restoring T cell homing. SLC is only prominently
expressed in the T cell zone of lymph nodes. SLC triggers integrin-dependent arrest of
CCR7-bearing T cells. Th1 and Th2 cells may home to different regions within the lymph
node, where CCR7 is more consistently expressed by Th1 cells. MIP-3 is not found on
HEV, but is present in the T cell area. It is thought to play a role in positional
localization rather than capture. Memory effector T cells lack CCR7, and can’t enter
lymph nodes. They home to inflammatory sites in non-lymphoid organs where they play
a role in antigen-specific immune responses.
Naïve B cells: CXCR5, a ligand for the chemokine BLC is found predominantly on
naïve B cells. BLC has been localized to the B cell follicles of lymph nodes, spleen, and

Peyer’s patches. Mice deficient in CXCR5 have diminished development of B cell
follicles. Ectopic expression of BLC in pancreatic islets in mice, results in local B cell
accumulation. Granulocytes don’t home to lymph nodes, presumably because they don’t
express CCR7 and CXCR5.
Chemokines control microenvironmental segregation within lymphoid
organs
Thus, the activation of B and T cells in lymph node HEV is different, and may initiate the
segregation into B and T cell zones. CXCR5 or CCR7-deficient animals have
disorganized lymphoid organs. This indicates that chemokines are key factors in the
development and maintenance of segregated microenvironments characteristic of
secondary lymphoid organs, and in the movement of lymphocytes in and out of these
areas. CCR7 and CXCR5 may be involved in the organization of T and B cell zones.
Balanced reponsiveness to chemokines from adjacent zones determines B
cell movement to the T cell zone
After B cells bind antigen they move to the boundary of B and T cell zones to interact
with T-helper cells. Antigen-engaged B cells have increased expression of CCR7, and
exhibit increased responsiveness to the T cell zone chemokines MIP3, and SLC. In mice
lacking MIP3 and SLC, or CCR7, B cells fail to move to the T cell zone after antigen
engagement. Increased expression of CCR7 by retroviral transfer is sufficient to direct B
cells to the T cell zone. Normally, antigen-stimulated B cells respond less strongly than T
cells to MIP3, and SLC, and are excluded from the central T cell zone. Conversely
overexpression of CXCR5 is sufficient to overcome antigen-induced B cell movement to
the T cell zone. Thus, lymphocyte localization can be determined by the balance of
responsiveness to chemoattractants made in separate but adjacent zones.
From Reif et al. Nature 416: 94-99,
2002
CCL19 = MIP3
CCL21 = SLC
CXCL13 = BLC
Homing of memory T cells and eosinophils to skin
Memory T cells, which express CD45RO, can enter any inflamed tissue to perform
antigen-specific immunosurveillance. They are selectively recruited after allergen
challenge of the skin. Eosinophils also accumulate in the skin.
Memory lymphocytes: CLA (specialized form of PSGL-1), which is a ligand for E-
selectin, is only found on activated memory skin homing T cells. E-selectin is induced de
novo on inflamed postcapillary endothelium, especially in skin. Recruitment of memory
CLA + T cells to the skin during allergic cutaneous inflammation involves interactions by

CLA binding E-selectin, LFA-1 to ICAM-1, VLA-4 to VCAM-1, which are stimulated
by endothelial-displayed TARC binding to CCR4 on leukocytes. Subsequent localization
within tissues may then be controlled by local production of other chemokines such as
MDC binding to CCR4, and CTACK binding to CCR10, and by VLA-1 and VLA-2.
Humans suffering from leukocyte adhesion deficiency syndrome-1 (LAD-1), due loss of
2 subunit, have frequent skin infections. The skin is devoid of neutrophils, and there are
reduced numbers of other leukocytes. CCR4 is highly expressed on CLA + memory T
cells. Its ligand TARC is present in venules of inflamed skin. TARC is expressed by
endothelial cells and stimulates T cell adhesion to ICAM-1. CTACK preferentially
activates homing to the skin of memory CLA + T cells. It is produced by keratinocytes
within the skin, and activates cells via CCR10. CCR4 and CCR10 may have overlapping
roles in cutaneous lymphocyte recruitment. CTACK may be transcytosed, and presented
on endothelium to support triggering of adhesion of skin-homing lymphocytes.
Eosinophils: Eosinophil migration into the skin during allergic cutaneous inflammation
involves P-selectin binding to PSGL-1, LFA-1 binding to ICAM-1, and VLA-4 binding
to VCAM-1, probably stimulated by eotaxin and eotaxin-3 binding to CCR3. Subsequent
localization may be mediated by CCR3-active chemokines, and by VLA-4, and VLA-6.
Human eosinophils express high levels of PSGL-1 and L-selectin. CCR3-active
chemokines such as RANTES, eotaxin, eotaxin-2, and MCP-4 are implicated in
eosinophil accumulation in skin. Intradermal injection of RANTES, or eotaxin-3 causes
selective and rapid accumulation of eosinophils.

Sunshine, vitamin D3, and dendritic cells imprint T cells to migrate to the
epidermis of the skin
The upper layer of the skin generates vitamin D3 from 7-dehydrocholesterol in response
to UVB rays. Dendritic cells in the skin express the vitamin D3 hydroxylases CYP27A1
and CYP27B1 which metabolize vitamin D3 to its active form 1,25(OH)2D3.
1,25(OH)2D3 stimulates memory or effector T cells to express the chemokine receptor
CCR10. CCR10-expressing T cells are attracted to the epidermis by the epidermal
chemokine CCL27 (CTACK), which is expressed by keratinocytes. It is thought this
system evolved to cope with frequent sun exposure and UV damage to the outer layers of
the skin.
Note: CCR10 is not required to recruit T cells to the dermis as this can be achieved by
CCR4. Rather CCR10 is required to attract T cells from the dermis to the epidermis.
Skin DCs migrate via the lymphatics to peripheral lymph nodes where they might imprint
naïve T cells with a skin homing phenotype (CLA + CCR4 hi 47 - ).
1,25(OH)2D3 inhibits the spontaneous upregulation of 47 on activated T cells, and
inhibits the induction of 47 and CCR9 by retinoic acid.
Leukocyte homing to the gut
Gut associated lymphoid tissues include Peyer’s patches (secondary lymphoid organs
resembling lymph nodes), mesenteric lymph nodes, and the lamina propria. Homing of
lymphocytes to Peyer’s patches and lamina propria involve interactions between LFA-1
and ICAM-1, 47 and MAdCAM-1, MAdCAM-1 and L-selectin, probably stimulated
by TECK binding to CCR9 or SLC binding to CCR7. Chemokines such as IP-10,
RANTES, MIP-1, and MIP-1 may influence lymphocyte accumulation within the
lamina propria under both inflamed and uninflamed conditions. A subset of gut-homing T

cells express CCR5 and CXCR3 and E7 and can migrate to the gut epithelium where
they interact with E-cadherin. For B cells, local production in Peyer’s patches of BLC
may be important. Accumulation of eosinophils involves LFA-1/ICAM-1, VLA-
4/VCAM-1, and 47/MAdCAM-1/L-selectin, perhaps influenced by eotaxin produced
by mononuclear cells.
Animals deficient in 7 integrins fail to accumulate T cells in the gastrointestinal tract,
and Peyer’s patches, because 47 is missing. SLC (which binds CCR7) stimulates
47-mediated adhesion of lymphocytes to MAdCAM-1. Defects in CCR7 or SLC
produce mice with reduced numbers of T cells in secondary lymphoid organs, including
Peyer’s patches. For B cells, BLC is important, as mice deficient in the BLC receptor
CXCR5 fail to develop normal Peyer’s patches. But SLC and BLC are not restricted to
the gut, hence are important in homing to lymph nodes in general. TECK, however, is
produced by small intestinal epithelial cells, but not by skin or lymph nodes, or by other
regions of the colon. It is mostly expressed in the crypt region most closely associated
with MAdCAM-1 expressing vessels. TECK has been detected on small intestinal
endothelium. Its receptor CCR9 is expressed on virtually all T cells in the small intestine,
and on memory CD4+ T cells, especially those expressing high levels of 47, whereas
it is not on other memory CD4 + T cells. The GI tract represents the largest reservoir of
eosinophils within the body. Eosinophils have the same pattern of adhesion molecules,
but don’t express either E7, or the chemokine receptors found on gut-homing T cells.
CCR3-active chemokines appear to be responsible for eosinophil accumulation. Eotaxindeficient
mice have few eosinophils within the villae of the intestine.

Vitamin A and dendritic cells imprint T and B cells to migrate to the small
intestine
The small intestine absorbs vitamin A as retinol and processes it to retinoic acid which is
present at high concentrations in the gut wall. Lumenal antigens in the gut are
internalized by M cells, and processed by DCs in the lamina propria. DCs in the gut are
induced by gut TGF- to express E7, and they express enzymes capable of processing
retinol to retinoic acid. E7+ DCs activate naive T and B cells in the mesenteric lymph
nodes (MLN) to express 47 and CCR9 in a retinoic acid-dependent fashion, thereby
imprinting the T and B cells with small intestine-homing properties. Retinoic acid
inhibits the induction of the skin homing receptor CLA.
Acknowledgement: Partly taken from http://hsc.virginia.edu/medicine/basicsci/biomed/ley/index.html,
R&D Systems; Springer TA Annu Rev Physiol 57: 827-872,
1995; Bochner BS J Allergy Clin Immunol 106: 817-828, 2000; Salmi M and Jalkanen S
Nature Rev Immunol 5: 760771, 2005; and Sigmundsdottir H, Butcher EC. Nat Immunol.
9: 981-7, 2008.
Table 1. Leukocyte integrins and their ligands

L2 Leukocytes ICAM-1, ICAM-2, ICAM-3
Telencephalin, Type I collagen
Landsteiner-Wiener (LW) blood
group glycoprotein
M2 Leukocytes ICAM-1, iC3b, factor X, galectin-3, Cfibrinogen
complement factor H, CD23,
neutrophil inhibitory factor,
oligodeoxynucleotides,
heparin, elastase, -glucans,
high molecular weight kininogen,
myeloperoxidase, azurocidin,
haptoglobin, denatured proteins,
Landsteiner-Wiener (LW) blood
group glycoprotein, fibrinogen,
Lipopolysaccarides, pertussis toxin
X2 Leukocytes iC3b, fibrinogen, CD23,
lipopolysaccarides
D2 Macrophages, eosinophils ICAM-3, VCAM-1
41 Leukocyte, muscle, VCAM-1, FN, MAdCAM-1
stimulated neutrophils,
neural crest cells,
fibroblasts
TSP, osteopontin, chondroitin
sulfate glycosaminoglycan
Propolypeptide of von Willebrand factor
casein, denatured albumin, 4 subunit
47 Leukocytes MAdCAM-1,VCAM-1, FN
E7 Activated leukocytes, IEL E-cadherin, RGD proteins?