ROLE OF C3A AND C5A IN THE ACTIVATION OF MAST-CELLS

Mast cells and basophils are known to be triggered by allergens via cr oss-linking with their high-affinity IgE-binding receptors, Fc epsilon RI. The anaphylatoxic activity of the complement-derived peptides C3a and C5a has been known for a long time; however, it has also been rep orted that serosal- and mucosal-type mast cells respond differently to peptidergic stimuli. The mechanism of mast cell activation by cross-l inking of Fc epsilon RI has been the subject of intensive studies in t he past few years, while the action mode of the anaphylatoxic compleme nt peptides has been revealed only recently. We report about a novel f unction of C3a: its inhibitory activity on IgE-mediated triggering of the mucosal RBL-2H3 cells. Surprisingly, the other anaphylatoxic pepti de C5a, which has been shown to be significantly more effective in sev eral biological assays, did not influence antigen-induced triggering o f the RBL-2H3 cell line at all.