Encyclopedia of Health and Medicine

gut-associated lymphoid tissue (GALT) 265
plantation provides the most successful circumstance
for preventing graft vs. host disease. When
precise HLA matching is not possible, screening for
and selectively removing some T-cell lymphocytes
(CD-4+ and CD-8+) from the donor organ that
carry antibodies likely to attack the recipient can
reduce the risk for graft vs. host disease. The risk
for graft vs. host disease is also higher for people
who receive blood stem cells extracted from
donated blood (rather than from bone marrow
donation), except cord stem cells extracted from
umbilical blood.
See also CLUSTERS OF DIFFERENTIATION; LEUKOCYTE;
LIVING WITH IMMUNE DISORDERS; LYMPHOCYTE; MUCOSA-
ASSOCIATED LYMPHOID TISSUE (MALT); STEM CELL; STEM
CELL THERAPY; SURGERY BENEFIT AND RISK ASSESSMENT.
granuloma An accumulation of granulocytes
(also called polymorphonuclear leukocytes
[PMNs]) and other cells that contain and enclose
an area of INFLAMMATION at the site of cell injury,
usually due to INFECTION. The effect is to “wall off”
the area so the infection cannot spread. The
resulting construction is fibrous (SCAR-like). Over
time the PATHOGEN causing the infection within the
granuloma dies but the granuloma remains. Granulomas
may form anywhere in the body.
CYTOKINES are instrumental in facilitating the
process of granuloma formation, directing the
actions of the involved immune cells.
Granulomas in the LUNGS commonly result from
HISTOPLASMOSIS and other fungal infections. Granuloma
inguinale is a sexually transmitted disease
(STD). Granulomas are also characteristic of
TUBERCULOSIS, Hansen’s disease (leprosy), and SAR-
COIDOSIS. Any underlying infectious disease
requires appropriate treatment. The doctor may
surgically remove granulomas that cause discomfort
or are unsightly. The granuloma itself usually
causes no problems and does not require treatment.
See also FUNGUS; GRANULOCYTE; LEUKOCYTE;
PHAGOCYTE; PHAGOCYTOSIS; SEXUALLY TRANSMITTED DIS-
EASES (STDS).
gut-associated lymphoid tissue (GALT) Loosely
organized, nonencapsulated clusters of LYMPH tissue
beneath the epithelium (tissue that forms the
mucous lining) of the gastrointestinal tract from
the ESOPHAGUS to the COLON. T-cell lymphocytes, B-
cell lymphocytes, and macrophages primarily
inhabit GALT. The role of GALT is to block NORMAL
FLORA BACTERIA (bacteria that are normally present
in the gastrointestinal tract to aid digestion) from
penetrating into other tissues or the BLOOD circulation.
GALT also helps prevent gastrointestinal
viruses from causing INFECTION. The presence of
GALT in the lining of the STOMACH increases with
aging. GALT also includes the small, nodelike lymphoid
structures called PEYER’S PATCHES that pepper
the SMALL INTESTINE. Peyer’s patches intensify the
presence of the IMMUNE SYSTEM and are the sites of
much ANTIBODY activity from B-lymphocytes.
See also LYMPH NODE; LYMPHOCYTE; MACROPHAGE;
MUCOSA-ASSOCIATED LYMPHOID TISSUE (MALT); NOSE-
ASSOCIATED LYMPHOID TISSUE (NALT); PATHOGEN; PHAGO-
CYTE; PHAGOCYTOSIS; SKIN-ASSOCIATED LYMPHOID TISSUE
(SALT); VIRUS.