DR Medhat MRCP

o Ig has 2 sides, 1 st one is the antigen-binding site which is formed by the variable
regions of both light & heavy chains while the 2 nd side (which is the tail) is
formed of the constant regions of both heavy chains (Fc part) which is attached
to the cell membrane.
o The heavy chains C part define the type & subtype of the Ig (IgA,IgG,IgM,….etc)
Class
IgM
(10%)
IgG
(75%)
IgA
(15%)
IgE
(O.O
O2%)
IgD
(1%)
Affinit
y
Low
-½ life
5 days
-High
-1/2
life 7-
23
days
-High
-1/2
life 5
days
-High
-1/2
life 2
Antibody classes and their functions
Type Function Complement
fixation
o Main class in serum 1ry (acute)
response
- Pentamer with 5
epitope-binding
sites
-Monometric forms
present on the
surface of B-cells
-Monomer with 2
epitope-binding sites
-Dimer with 4
epitope-binding sites
-monomer with 2
epitope-binding sites
days
-Low -monomer with 2
epitope-binding sites
o Main class in serum 2ndry
(chronic)response
o Bind to Fc receptors on
phagocytes is important in Abmediated
inflammation.
o Bind to Fc receptors on NK-cells
for Ab-dependent cytotoxicity
o The only Ig that can cross
placenta to the fetal circulation.
o Mediates hyperacute renal
هام جدا transplant rejection
o Secreted across mucosal surface
(present in saliva,tears,milk,other
body secretions)
o ++ mast cells & basophils via its
Fc receptors.
o Important in allergic reactions &
reaction to parasites
o Surface marker expressed during
development of B-cells
eliminate self-reacting B-cells &--
autoimmunity
Fix
complement
(++ classical
هام pathway)
Fix
complement
(++ classical
pathway)
++
Alternative
pathway
Doesn`t fix
complement
Doesn`t fix
complement
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