The B4B6 antibody recognizes human CD172b also known as signal-regulatory protein beta, and SIRP-beta. CD172b is a member of the signal regulatory protein family and immunoglobulin superfamily. CD172b contains a single pass transmembrane region with immunoglobulin-like domains and unlike CD172a, this receptor lacks a cytoplasmic SHP-2 binding domain. CD172b is a disulfide-linked homodimer with a predicted molecular weight of approximately 43 kD. Two isoforms of CD172b are produced by alternative splicing. CD172b is expressed on myeloid cells including monocytes and dendritic cells where it functions in the negative regulation of tyrosine-kinase coupled signaling processes. CD172b has been shown to regulate neutrophil transepithelial migration. CD172b interacts with DAP12 and Syk kinase (through TYROBP). The B4B6 antibody has been shown to be useful for flow cytometry.