Dr. Murai Éva szerk.: Parasitologia Hungarica 22. (Budapest, 1989)

different pathways of mast cell activation. Perhaps the most important is the cross linking of IgE receptors of the mast cell surface. These receptors bind IgE molecules which mediate bridging by specific antigen. Receptor cross linking leads to cell activation and release of mediators. Other pathways of mast cell activation are the subject of current research. Mast cell mediators include those that are preformed, such as vasoactive amines (histamine, serotonin), proteoglycans (heparin), proteolytic enzymes (RMCPI, RMCPII), as well as those that are generated de novo after activation, like prostaglandins, leukotrienes, etc. (Fig. 2). Mast cell mediators have profound effects on many of the cells known to be active in antiparasite immunity. Histamine promotes recruitment of T cells, neutrophils, eosinophils, basophils, macrophages at the site of Infection, and activates suppressor T cells to suppress both T cell and B cell responses. Serotonin has marked effects on vascular permeability and lymphocyte function. These biogenic amines obviously play a powerful role in the immediate hypersensitivity reaction, in the pathology on inflammation and have extensive immunoregulatory effects (LEE, SWIETER and BE FUS 1984). Thus they exert manifold indirect effect on worm survival. However, there is only a weak evidence to suggest that these PREFORMED MEDIATORS Readily eluted following activation Histamine 5-Hydroxytryptamine (serotonin) Chemotactic factors for neutrophils and eosinophils Activators of kinin, complement and clotting systems Vasoactive intestinal peptide Prostaglandin-generating factor of anaphylaxis Granule-associated Proteoglycans: heparin, chondroitin sulfates Proteolytic enzymes: tryptase, serine proteases Inflammatory factor of anaphylaxis MEDIATORS GENERATED ON ACTIVATION Prostaglandins Hydroperoxyeicosatetraenoic acids (HPETEs) Hydroxyeicosatetraenoic acids (HETEs) Leukotrienes Platelet-activating factor Fig. 2 Mast cell mediators (Barrett and Metcalf, 1988)