Signal-regulatory protein beta 1 is a member of the signal-regulatory-protein (SIRP) family, and also belongs to the immunoglobulin superfamily. SIRP family members are receptor-type transmembrane glycoproteins known to be involved in the negative regulation of receptor tyrosine kinase-coupled signaling processes. This protein was found to interact with TYROBP/DAP12, a protein bearing immunoreceptor tyrosine-based activation motifs. This protein was also reported to participate in the recruitment of tyrosine kinase SYK. Alternatively spliced transcript variants have been found for this gene. The signal regulatory protein-beta1 (SIRPbeta1) is a DAP12-associated transmembrane receptor expressed in a subset of hematopoietic cells. Recently, it was shown that peritoneal macrophages express SIRPbeta1, which positively regulated phagocytosis.