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major histocompatibility complex class II deficiency 478 mammals
major histocompatibility complex class II deficiency
(MHC II deficiency)
A condition characterized by the lack of MHC class II
expression. It leads to a severe defect in both cellular and
humoral immune responses to foreign antigens and is consequently
characterized by an extreme susceptibility to viral,
bacterial, fungal, and protozoal infections, primarily of the
respiratory and gastrointestinal tracts. Severe malabsorption
with failure to thrive ensues, often leading to death in early
childhood. Also called bare lymphocyte syndrome type II.
major histocompatibility complex (MHC) molecule
MHC locus-encoded heterodimeric membrane proteins
used by T lymphocytes to recognize antigen. They are
divided into two structural types designated class I and
class II. Most nucleated cells of the body express MHC
class I molecules, which bind peptides derived from
cytosolic proteins and are recognized by CD8 + T lymphocytes.
The distribution of MHC class II molecules is
more restricted, confined mostly to professional antigenpresenting
cells that bind peptides from enocytosed proteins
recognized by CD4 + T cells.
major histocompatibility complex restriction
Refer to MHC restriction.
major histocompatibility system
Refer to major histocompatibility complex.
Makari test
A no-longer-recommended assay that consisted of preparing
an extract from a patient’s tumor, incubating it with the
patient’s serum, and inoculating it into the skin, where it
would induce an immediate skin reaction.
malaria
A disease induced by protozoan parasites (Plasmodium
species) with a complex life cycle in a mosquito and a
vertebrate host. Four species are responsible for human
malaria. Numerous immunogenic proteins are formed at
each morphologically distinct stage in the life cycle. The
asexual stage in the blood stream causes the disease. The
parasite employs various mechanisms to evade a protective
immune response; however, immunity against the parasite
and the disease eventually develops from repeated exposure.
Malaria vaccine development is in progress.
malaria vaccine
Although no vaccine is presently effective against malaria,
several candidates are under investigation including an
immunogenic but nonpathogenic Plasmodium sporozoite
attenuated by radiation. Circumsporoite (CS) proteins
combined with sporozoite surface protein 2 (SSP-2) are
immunogenic. Murine studies have shown the development
of transmission-blocking antibodies following immunization
with vaccinia into which the P. falciparum surface 25-kDa
protein designated Pfs25 has been inserted. Attempts have
Signal
Met
100
Repeats
200
Asn-Ala-Asn-Pro Asn-Val-Asp-Pro
Circumsporate protein of malaria.
been made to increase natural antibodies against CS protein
to prevent the prehepatoinvasive stage. The high mutability of
P. falciparum makes prospects for an effective vaccine dim.
malignant
Leading to death, e.g., a malignant neoplasm.
malignant conversion
Stage IV of carcinogenesis. The progressive accumulation
of mutations in neoplastic cells rendering it a malignant
tumor with total lack of growth regulation. The tumor may
become invasive and metastatic.
malignant transformation
Alterations in a cell render it neoplastic. A neoplasm characterized
by uncontrolled growth, invasive properties, and metastatic
potential. Left untreated, it can lead to death of the host.
malignolipin (historical)
A substance claimed to be specific for cancer and detectable
in blood early in the course of the disease. This concept is
no longer considered valid. Malignolipin is comprised of
fatty acids, phosphoric acid choline, and spermine. When
injected into experimental animals, it can produce profound
anemia, leukopoiesis, and cachexia.
MALT
Refer to mucosa-associated lymphoid tissue.
mammals
Compared with lower forms, mammals develop additional
immunoglobulin classes, e.g., IgD, IgG, and subclasses.
They also manifest increased diversity of major histocompatibility
complex (MHC) antigens. Three distinct
recognition systems are recognized in mammals. These
include antibody, on B cells only, the T cell receptor, on
T lymphocytes only, and on a spectrum of cells (MHC),
all of whose genes evolved from a common ancestor. The
close similarity of murine and human immune systems has
300
Mammals (man and mouse).
Th2R
Thrombospondin
homology
400
Cys
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Cys Cys
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