Human cardiac mast cells in anaphylaxis.

Human heart mast cells (HHMC), by elaborating vasoactive mediators, cytokines and chemokines, are the main primary effector cells of anaphylaxis. Mast cells have been identified perivascularly, close to myocytes and in the arterial intima in human heart tissue. Mast cells isolated from human heart tissue (HHMC) of patients undergoing cardiac transplantation express high-affinity receptors for IgE (FcepsilonRI) and C5a receptors. Activation of HHMC in vitro with anti-IgE or anti-FcepsilonRI induced the release of preformed mediators (histamine, tryptase, chymase, and renin) and the de novo synthesis of LTC(4) (approximately =18 ng/l0(6) cells) and PGD(2) (approximately =18 ng/l0(6) cells). Complement is activated and anaphylatoxin forms during anaphylaxis. C5a causes rapid release of histamine and tryptase from HHMC. These cells are activated in vitro by therapeutic (general anesthetics, protamine, etc.) and diagnostic agents (radiocontrast media, etc.) which can cause anaphylactoid reactions. Low concentrations of histamine and cysteinyl leukotrienes given to subjects undergoing diagnostic catheterization caused significant systemic and coronary hemodynamic effects. These results indicate that HHMC probably have a role in anaphylactic reactions.