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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)
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).
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.
Migration inhibition factor (MIF)
A lymphokine that inhibits the motility of macrophages in culture.
Minor histocompatibility antigens
These antigens, encoded outside the MHC, are numerous, but do not generate rapid graft rejection or primary responses of T cells in vitro. They do not serve as restricting elements in cell interactions.
Mitogen
A substance that stimulates the proliferation of many different clones of lymphocytes.
Mixed lymphocyte reaction (MLR)
When lymphocytes from two individuals are cultured together, a proliferative response is generally observed, as the result of reactions of T cells of one individual to MHC antigens on the other individual's cells.
Monoclonal
Literally, coming from a single clone. A clone is the progeny of a single cell. In immunology, monoclonal generally describes a preparation of antibody that is monogenous, or cells of a single specificity.
Monocyte
Large circulating white cell, 2-10% of total white cells, phagocytic, indented nucleus. Migrates to tissues, where it is known as a macrophage.
Monokines
Soluble substances secreted by monocytes, which have a variety of effects on other cells.
Myeloma
A tumor of plasma cells, generally secreting a single species of immunoglobulin.
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