MARKERS OF MAST-CELL DEGRANULATION

Mast cells are the primary effector cells of immediate hypersensitivit y reactions in humans. Upon mast cell activation both preformed and ne wly synthesized mediators are secreted. Histamine can be measured by f luorometric assays, radioenzymatic assays, and immunoassays. These met hods have been applied to plasma and urine to detect histamine that ha d been released in vivo and to release histamine in vitro from basophi ls and mast cells. Another mast cell constituent is tryptase, which is a more selective marker of mast cells, because negligible amounts are found in basophils. beta-Tryptase is stored in secretory granules and is actively released when mast cells degranulate. alpha-Protryptase r emains in the proenzyme form and is constitutively released from mast cells, and consequently its level in serum reflects total numbers of m ast cells. alpha-Protryptase levels are elevated in serum at baseline in subjects with systemic mastocytosis, whereas beta-tryptase is eleva ted in serum from subjects with systemic anaphylaxis. These markers se rve as precise clinical indicators of the involvement of mast cells in human disease. (C) 1997 Academic Press.