Figure 1.
Adhesive interactions of SIRPα-CD47 on cell surfaces. Based on mouse studies, binding between CD47's Ig domain on RBCs and the N-terminal Ig domain of SIRPα (or SHPS-1, P84) on phagocytes is thought to trigger clustering of SIRPα. Phosphorylation events at SIRPα's cytoplasmic tail are then believed to ultimately signal “self” and inhibit phagocytosis of RBCs. This occurs through tyrosine phosphorylation of SIRPα5 and subsequent recruitment of phosphatases (SHP-1 predominantly).7
