factors that begins with ANTIBODY–ANTIGENbinding)
is the primary alert mechanism that activates the
mononuclear phagocyte system. Monocytes and
macrophages work in a coordinated fashion, com-
municating via CYTOKINES (cell-originated bio-
chemical messages) with other cells involved in
the IMMUNE RESPONSE.
For further discussion of the mononuclear
phagocyte system within the context of the struc-
tures and functions of the immune system, please
see the overview section “The Immune System
and Allergies.”
See also B-CELL LYMPHOCYTE; CELL STRUCTURE AND
FUNCTION; GENE; GRANULOCYTE; MACROPHAGE; MONO-
CYTE; NATURAL KILLER(NK) CELL; PHAGOCYTE; PHAGOCY-
TOSIS; T-CELL LYMPHOCYTE.
mucosa-associated lymphoid tissue (MALT) A
loosely organized collection of LY M P H tissue that
underlies and integrates with epithelial tissue (the
lining of mucous membranes) throughout the
body. MALT reinforces the body’s immune pres-
ence and response in areas of the body that pro-
vide direct interface with the external
environment. These areas, such as the gastroin-
testinal tract and the LUNGS, are most vulnerable to
breaches that could allow pathogens to enter the
body to cause INFECTION.
MALT contains clusters of phagocytic cells such
as macrophages and dendritic cells, which con-
sume cellular debris, as well as T-cell lymphocytes
and B-cell lymphocytes. T-cell lymphocytes attack
and kill invading pathogens, and B-cell lympho-
cytes produce antibodies to protect against future
invasion by the same pathogens. There are several
types of MALT; each has specific functions, accord-
ing to its location in the body. Among them are
- BRONCHUS-ASSOCIATED LYMPHOID TISSUE (BALT),
which strengthens the body’s defense against
INFLUENZAand PNEUMONIA - GUT-ASSOCIATED LYMPHOID TISSUE (GALT), which
helps protect against invasion by gastrointesti-
nal viruses - NOSE-ASSOCIATED LYMPHOID TISSUE(NALT), which
intensifies the body’s resistance to airborne
viruses such as those that cause COLDS- SKIN-ASSOCIATED LYMPHOID TISSUE (SALT), which
helps block BACTERIA, fungi, and other
pathogens from passing through microscopic
breaks in the SKIN - VASCULAR-ASSOCIATED LYMPHOID TISSUE (VA LT),
which infiltrates the epithelium of the BLOOD
vessels
- SKIN-ASSOCIATED LYMPHOID TISSUE (SALT), which
MALT may be the site of solid tumors that
develop in LYMPHOMA (sometimes called MALT
lymphoma). The most common MALT site for
such an occurrence is the gastrointestinal tract.
Researchers believe these lymphomas develop
when a constant assault, such as a persistent infec-
tion, engages the MALT site. B-cell lymphocytes
accumulate to fight the infection. When their
accumulation persists over time, which is abnor-
mal, the B-cell lymphocytes turn cancerous. The
connection with MALT lymphomas that arise from
GALT is HELICOBACTER PYLORIinfection, which also
has a strong connection to STOMACH CANCER.
Researchers believe H. pylorimay account for 85
percent or more of gastrointestinal MALT lym-
phomas, many of which grow in the STOMACH.
Treatment is highly successful when the diagnosis
of MALT lymphoma occurs early in the CANCER’s
development because the tumors grow slowly and
lack aggression in spreading.
For further discussion of MALT within the con-
text of the structures and functions of the immune
system, please see the overview section “The
Immune System and Allergies.”
See also ANTIBODY; B-CELL LYMPHOCYTE; FUNGUS;
LYMPHOCYTE; MACROPHAGE; METASTASIS; MONONUCLEAR
PHAGOCYTE SYSTEM; PATHOGEN; PHAGOCYTE; PHAGOCY-
TOSIS; T-CELL LYMPHOCYTE; VIRUS.multiple chemical sensitivity syndrome A con-
stellation of symptoms that result from exposure
to common chemicals at levels that do not nor-
mally cause response or reaction. Multiple chemi-
cal sensitivity syndrome is difficult to diagnose
and treat. Symptoms are often broad ranging.
There remains disagreement among medical
experts (doctors and researchers) about the diag-
nostic criteria and causes of the syndrome. Some
believe multiple chemical sensitivity syndrome is a
component of GENERALIZED ANXIETY DISORDER(GAD)284 The Immune System and Allergies