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• Immunology Terms

- M -

• 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.