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μ heavy chain disease 512 mucosal lymphoid follicles
μ heavy chain disease
A type of myelomatosis in which aberrant monoclonal
immunoglobulin μ chains are present in serum but not
in urine, and Bence–Jones proteins are present in urine.
Although very rare, this condition may be associated with
chronic lymphocytic leukemia or reticulum cell sarcoma.
Vacuolated plasma cells have been demonstrated in the
bone marrow and are very suggestive of the diagnosis of
μ heavy chain disease. The μ chains produced by bone
marrow plasma cells have deletions in the variable regions
and involve the C H1 domain but have a normal sequences in
the C H2 domain. Light chains synthesized by these patients
are not incorporated into molecular IgM; therefore, these
individuals demonstrate distinct failures in the assembly
of immunoglobulin molecules. Heavy and light chains
have different electrophoretic motilities, which becomes an
important observation in establishing a diagnosis of μ heavy
chain disease by electrophoresis.
mucin
Heavily glycosated serine- and threonine-rich proteins that
serve as ligands for selectins.
mucocutaneous candidiasis
Cellular immunodeficiency is associated with this chronic
Candida infection of the skin, mucous membranes,
nails, and hair, with about 50% of patients manifesting
endocrine abnormalities. Cell-mediated immunity
to Candida antigens alone is absent or suppressed. The
individual manifests anergy following the injection of
Candida antigen into the skin. Immunity to other infectious
agents, including other fungi, bacteria, and viruses,
is not impaired. The B cell limb of the immune response,
even to Candida antigens, does not appear to be affected.
The antibody response to Candida and other antigens
is within normal limits. The relative numbers of both T
and B lymphocytes are normal, and immunoglobulins
are at normal or elevated levels. Four clinical patterns
have been described. The most severe is known as early
chronic mucocutaneous candidiasis with granuloma and
hyperkeratotic scales on the nails or face. This condition
has associated endocrinopathy in about 50% of the cases.
The second type is late-onset chronic mucocutaneous
candidiasis, which involves the oral cavity or occasionally
the nails. The third form is transmitted as an autosomalrecessive
trait and is usually not associated with endocrine
abnormalities. It is a mild to moderately severe disorder.
The fourth form is known as juvenile familial polyendocrinopathy
with candidiasis, which may be associated with
hypoparathyroidism with or without Addison’s disease.
Those individuals in whom endocrinopathy is associated
with mucocutaneous candidiasis may demonstrate autoantibodies
against the endocrine tissue involved. In addition
to the immunologic abnormalities described above, there
is diminished formation of lymphokines (e.g., macrophage
migration inhibitory factor, or MIF) directed against
Candida antigens. Recommended treatment includes antimycotic
agents and immunologic intervention designed to
improve resistance of the host.
mucocutaneous lymph node syndrome
Refer to Kawasaki’s disease.
mucosa
The mucus-secreting epithelial layers that cover the exterior
surfaces of the respiratory, gastrointestinal, and urogenital
Bronchus
Bronchial
patch
Lymph
vessels
Mediastinal
node
Cell traffic.
Lacrimal and salivary glands
GU tract
Lactating breast
Liver/biliary tract
Intestine
Blood
vessel
Mesenteric
node
Peyer’s
patch
tracts. The conjunctiva of the eye and the mammary glands
also belong to this classification.
mucosa homing
The selective return of immunologically reactive lymphoid
cells that originated in mucosal follicles, migrated to other
anatomical locations, and then returned to their site of
origin in mucosal areas.
mucosa-associated lymphoid tissue (MALT)
Extranodal lymphoid tissue associated with the mucosa
at various anatomical sites including the skin (SALT),
bronchus (BALT), gut (GALT), nasal-associated lymphoid
tissue (NALT), breast, and uterine cervix. MALTs provide
localized or regional immune defense, as they are in immediate
contact with foreign antigenic substances, thereby
differing from the lymphoid tissues associated with lymph
nodes, spleen, and thymus. Secretory or exocrine immunoglobulin
A (IgA) is associated with the MALT system of
immunity. The lymphoid tissues comprising MALT include
intraepithelial lymphocytes, principally T lymphocytes
together with B cells beneath the mucosal epithelia and in
the lamina propria.
mucosal immune system
Aggregates of lymphoid tissues or lymphocytes near
mucosal surfaces of the respiratory, gastrointestinal, and
urogenital tracts that protect against microorganisms
gaining access to the body through mucosal surfaces. The
mucosal immune system is comprised of mucosa-associated
lymphoid tissues that consist of lymphocyte and accessory
cell aggregates in the epithelia and lamina propria of
mucosal surfaces. There is local synthesis of secretory IgA
and T cell immunity at these sites. Research in this field is
so extensive that the Society for Mucosal Immunology was
established to represent interests in this area.
mucosal immunity
Refer to mucosal immune system.
mucosal lymphoid follicles
These structures include Peyer’s patches in the small
intestine and pharyngeal tonsils. The appendix and other
areas of the gastrointestinal tract and respiratory tract
contain similar aggregates of lymphoid cells. Germinal
centers at the centers of lymphoid follicles have an abundance
of B cells. CD4 + T cells are present in interfollicular
regions of Peyer’s patches. One half to three quarters
of the lymphocytes in murine Peyer’s patches are B cells,