plantation provides the most successful circum-
stance 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 INFLAMMATIONat 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 PATHOGENcausing the infection within the
granuloma dies but the granuloma remains. Gran-
ulomas 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 LUNGScommonly result from
HISTOPLASMOSISand other fungal infections. Granu-
loma 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 discom-
fort or are unsightly. The granuloma itself usually
causes no problems and does not require treat-
ment.
See also FUNGUS; GRANULOCYTE; LEUKOCYTE;
PHAGOCYTE; PHAGOCYTOSIS; SEXUALLY TRANSMITTED DIS-
EASES(STDS).gut-associated lymphoid tissue (GALT) Loosely
organized, nonencapsulated clusters of LY M P Htis-
sue beneath the epithelium (tissue that forms the
mucous lining) of the gastrointestinal tract from
the ESOPHAGUSto 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 BLOODcircula-
tion. GALT also helps prevent gastrointestinal
viruses from causing INFECTION. The presence of
GALT in the lining of the STOMACHincreases with
aging. GALT also includes the small, nodelike lym-
phoid structures called PEYER’S PATCHESthat pepper
the SMALL INTESTINE. Peyer’s patches intensify the
presence of the IMMUNE SYSTEMand are the sites of
much ANTIBODYactivity 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.gut-associated lymphoid tissue (GALT) 265