Lankester A C, van Schijndel G M, Cordell J L, van Noesel C J, van Lier R A
Department of Clinical Viro-Immunology, The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
Eur J Immunol. 1994 Apr;24(4):812-6. doi: 10.1002/eji.1830240406.
On human B cells the antigen receptor complex is composed of the membrane form of the immunoglobulin molecule and the non-covalently associated Ig alpha/beta heterodimer. A small subpopulation of normal B cells and chronic lymphocytic leukemia B cells express (analogous to T cells) the transmembrane molecule CD5, a counterstructure of B cell-specific CD72. Numbers of CD5+ B cells are increased in several physiological and pathological conditions. Moreover, CD5+ B cells are being held responsible for the production of autoreactive antibodies and seem to have signaling characteristics distinct from conventional B cells. On T cells, CD5 associates with the T cell receptor CD3 complex and ligation of CD5 leads to the generation of co-stimulatory signals, that act on T cell activation. We here demonstrate that CD5 is associated with the B cell receptor (BCR) complex and serves as substrate for BCR-induced tyrosine kinase activity. Hence, CD5+ B cells have a unique potential to modulate BCR signals.
