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Major histocompatibility complex (MHC)
Major histocompatibility complex (MHC) A cluster of genes on chromosome 6 in humans, encoding cell surface molecules that are polymorphic and that code for antigens which lead to rapid graft rejection between members of a single species which differ at these loci. Several classes of protein such as MHC class I and II proteins are encoded in this region. These in humans, are known as 'Human leukocyte antigens' (HLA).
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Cluster
In epidemiology, an aggregation of cases of a disease or another health-related condition, such as a cancer or birth defect, closely grouped in time and place. The number of cases in the cluster may or may not exceed the expected number. This is determined by cluster analysis, a set of statistical methods used to analyze clusters.
Genes
Basic, functional units of heredity, each occupying a specific place on a chromosome.
Chromosome
A structural unit within a eukaryotic nucleus that carries genes. A chromosome consists of a long, continuous strand of DNA and associated proteins.
Cell
Fundamental structural unit of all life. The cell consists primarily of an outer plasma membrane, which separates it from the environment; the genetic material (DNA), which encodes heritable information for the maintainance of life; and the cytoplasm, a heterogeneous assemblage of ions, molecules, and fluid.
Code
The genetic code is the correspondence between the triplet of bases in DNA with the amino acids.
Antigens
Substances that cause an immune response in the body. The body "sees" the antigens as harmful or foreign. To fight them, the body produces antibodies, which attack and try to eliminate the antigens.
Graft
A piece of skin or other tissue used as a transplant.
Rejection
The process by which the body tries to get rid of a transplanted organ or tissue by producing antibodies. Immunosuppressive drugs help to prevent rejection.
Protein
Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of a-amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins, and each protein has a unique genetically defined amino acid sequence which determines its specific shape and function. Their roles include enzymatic catalysis, transport and storage, coordinated motion, nerve impulse generation and many others.
Leukocyte
White blood cell.
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Mayo Clinic diet
A nutritional diet developed by the prestigious Mayo Clinic.
Mammography
An X-ray procedure using a special low irradiation technique to detect abnormal change in breast tissue. Its main use is to detect breast lumps that are too small to be found during breast self examination or physical examination. The higher the level of estrogen (and possibly progestin) the more dense breast tissue is and the less likely that a mammogram will see abnormal tissue. It has many false positive readings meaning that there is no cancer yet the test was abnormal.
Motor neuron disease
Diseases characterized by a selective degeneration of the motor neurons of the spinal cord, brainstem, or motor cortex. Clinical subtypes are distinguished by the major site of degeneration. In amyotrophic lateral sclerosis there is involvment of upper, lower, and brainstem motor neurons. In progressive muscular atrophy and related syndromes the motor neurons in the spinal cord are primarily affected. With progressive bulbar palsy, the initial degeneration occurs in the brainstem. In primary lateral sclerosis, the cortical neurons are affected in isolation.
Macrophage
A large phagocytic cell of the mononuclear series found within tissues. Properties include phagocytosis, and antigen presentation to T cells.
Macrophage-activating factor (MAF)
Actually several lymphokines, including interferon, released by activated T cells, which together induce activation of macrophages, making them more efficient in phagocytosis and cytotoxicity.
Major histocompatibility complex (MHC)
Mast cell
Tissue located cell probably derived from basophils. Possesses receptor for Fc of IgE. Participates in 'Immediate hypersensitivity' reactions.
Memory
In the immune system, memory denotes an active state of immunity to a specific antigen, such that a second encounter with that antigen leads to a larger and more rapid response.
MHC class I molecule
A molecule encoded to genes of the MHC which participates in antigen presentation to cytotoxic T (CD8+) cells.
MHC class II molecule
A molecule encoded by genes of the MHC which participates in antigen presentation to helper T (CD4+) cells.
MHC restriction
The ability of T lymphocytes to respond only when they 'see' the appropriate antigen in association with "self" MHC class I or class II proteins on the antigen presenting cells.
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