mucosal immune system The immune system that protects internal mucosal surfaces (such as the linings of the gut, respiratory tract, and urogenital tracts), which are the site of entry for virtually all pathogens and other antigens. See also mucosa-associated lymphoid tissue.
mucosal mast cells Specialized mast cells present in mucosa. They produce little histamine but large amounts of prostaglandins and leukotrienes.
mucosal tolerance The suppression of specific systemic immune responses to an antigen by the previous administration of the same antigen by a mucosal route.
mucus Sticky solution of proteins (mucins) secreted by goblet cells of internal epithelia, forming a protective layer on the epithelial surface.
multiple sclerosis A neurological autoimmune disease characterized by focal demyelination in the central nervous system, lymphocytic infiltration in the brain, and a chronic progressive course.
multipotent progenitor cells (MPPs) Bone marrow cells that can give rise to both lymphoid and myeloid cells but are no longer self-renewing stem cells.
muramyl dipeptide (MDP) A component of the peptidoglycan of most bacteria that is recognized by the intracellular sensor NOD2.
muromomab A mouse antibody against human CD3 used to treat transplant rejection; this was the first monoclonal antibody approved as a drug in humans.
mutualism A symbiotic relationship between two organisms in which both benefit, such as the relationship between a human and its normal resident (commensal) gut microorganisms.
Mx (myxoma resistant) proteins Interferon-inducible proteins required for cellular resistance to inﬂuenza virus replication.
myasthenia gravis An autoimmune disease in which autoantibodies against the acetylcholine receptor on skeletal muscle cells cause a block in neuromuscular junctions, leading to progressive weakness and eventually death.
mycophenolate An inhibitor of the synthesis of guanosine monophosphate that acts as a cytotoxic immunosuppressive drug. It acts by killing rapidly dividing cells, including lymphocytes proliferating in response to antigen.
mycophenolate mofetil Pro-drug used in cancer treatment that is metabolized to mycophenolate, and inhibitor of inosine monophosphate dehydrogenase, thereby impairing guanosine monophosphate, and thus DNA, synthesis.
MyD88 An adaptor protein that functions in signaling by all TLR proteins except TLR3.
myeloid Refers to the lineage of blood cells that includes all leukocytes except lymphocytes.
myeloid-derived suppressor cells (MDSCs) Cells in tumors that can inhibit T-cell activation within the tumor.
myelomonocytic series Innate immune cells derived from myelomonocytic bone marrow precursors, including neutrophils, basophils, eosinophils, monocytes, and dendritic cells.
NADPH oxidase Multicomponent enzyme complex that is assembled and activated in the phagolysosome membrane in stimulated phagocytes. It generates superoxide in an oxygen-requiring reaction called the respiratory burst.
NAIP2 An NLR protein that, together with NLRC4, recognizes the PrgJ protein of the Salmonella typhimurium type III injection system to activate an inﬂammasome pathway in response to infection.
NAIP5 An NLR protein that, together with NLRC4, recognizes intracellular ﬂagellin to activate an inﬂammasome pathway in response to infection.
naive lymphocytes T cells or B cells that have undergone normal development in the thymus or the bone marrow but have not yet been activated by foreign (or self) antigens.