CD172b, the signal-regulatory protein beta (SIRP beta) is a disulfide-linked homodimer expressed on myeloid cells including monocytes and dendritic cells. Similarly to CD172a, it serves as a negative regulator of tyrosine kinase-coupled signaling processes. Unlike CD172a, the CD172b protein does not possess the cytoplasmic domain, but instead its transmembrane domain can interact with another transmembrane protein DAP-12, which contains ITAM sequences in its intracellular domain and links CD172b to the downstream signaling molecules. The result is e.g. regulation of neutrophil transepithelial migration.