B-Cell Differentiation Antigen CD72 (CD72) is a single-pass type II membrane protein. CD72 exists as a disulfide-linked homodimer and contains one C-type lectin domain. CD72 is expressed on B lineage cells, NK cells, monocytes, dendritic cells, and mast cells. CD72 is a ligand for CD5. CD72 associates with CD5, interacts with PTPN6/SHP-1 and plays a role in B-cell proliferation and differentiation. CD72 associates with CD79A in the B cell antigen receptor (BCR) complex following antigen stimulation and dampens BCR signaling through interactions with the phosphatase SHP-1.