CALCIUM SIGNALING INITIATED BY CR-1 (CD35) CROSS-LINKING IS MEDIATED BY PHAGOCYTE FC-GAMMA RECEPTORS IN CIS

We have examined the role of complement receptor type 1 (CR1; CD35) in generating intracellular signals in phagocytic cells, particularly hu man neutrophils. We find that crosslinking of CR1 alone fails to resul t in an increase in intracellular ionized calcium [Ca2+](i). However, IgG bound to CR1 is able to interact with Fc gamma receptors to stimul ate increases in [Ca2+](i). By examining signals generated in mixed po pulations of cells, we determined that calcium increases are observed only when CR1 and Fc gamma receptors are engaged on the same cell. Fun ctional interactions between complement receptors and receptors for im munoglobulin G may promote clearance of pathogenic bacteria and fungi that bind limited quantities of complement and IgG. (C) 1995 Academic Press, Inc.