Inhibition of IgE-mediated triggering of mast cells by complement-derived peptides interacting with the Fc epsilon RI

Mucosal type mast cells, in contrast to the serosal type ones, do not respo nd to cationic agents, or to the complement-derived peptides C3a and C5a [1 ]. Earlier we have found that while C3a does not activate the rat mucosal t ype mast cells (line RBL-2H3), it strongly inhibits the IgE-mediated trigge ring of these cells, by interfering with the Fc epsilon RI-initiated signal ing pathway [2]. In the present study we further investigated the mechanism of this process. It is shown, that C3a interacts with the beta-chain of th e Fc epsilon RI complex. Binding of the complement peptide to the cells app arently causes a decrease in the proximity of the IgE-binding Fc epsilon RI . Investigating certain sequences of C3a we found that the inhibition is ca used by the C-terminal sequences of the complement-peptide, ranging from po sitions 56 to 77 and also by a shorter sequence, ranging from positions 56 to 64. The inhibitory effect of these peptides was observed both in the cas e of RBL-2H3 cells and mouse bone marrow derived mast cells. (C) 1999 Elsev ier Science B.V. All rights reserved.