title: CD5 is associated with the human B cell antigen receptor complex.
abstract: 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.
authors.affiliation: Department of Clinical Viro-Immunology, The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
authors.forename: A C
authors.initials: AC
authors.lastname: Lankester
authors.forename: G M
authors.initials: GM
authors.lastname: van Schijndel
authors.forename: J L
authors.initials: JL
authors.lastname: Cordell
authors.forename: C J
authors.initials: CJ
authors.lastname: van Noesel
authors.forename: R A
authors.initials: RA
authors.lastname: van Lier
mesh_terms: D015703:Antigens, CD / Q000032:analysis*; D001402:B-Lymphocytes / Q000737:chemistry*; D018956:CD5 Antigens; D006801:Humans; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology; D011947:Receptors, Antigen, B-Cell / Q000032:analysis*
chemical_list: D015703:Antigens, CD; D018956:CD5 Antigens; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011947:Receptors, Antigen, B-Cell