title: Monoclonal antibodies to murine CD40 define two distinct functional epitopes.
abstract: Two rat IgG2a antibodies which define distinct epitopes on murine CD40 have been generated. These antibodies specifically bind recombinant murine CD40 expressed on L cells, and the soluble extracellular domain of murine CD40 coated onto microtiter plates. Both antibodies bind B220+ but not B220 murine spleen cells, and immunoprecipitate a 45-kDa protein from the surface of purified murine splenic B cells. These antibodies exhibit separate functional properties, consistent with the notion that they define two distinct CD40 epitopes. One of the monoclonal antibodies (designated 1C10) directly induces a specific proliferative response from mature murine B cells, up-regulates several B cell surface antigens, and rescues immature B lymphoma cells from anti-IgM-induced growth arrest. The other monoclonal antibody (designated 4F11) exhibits none of these properties, but is capable of synergizing with suboptimal amounts of either anti-IgM antibodies or the 1C10 agonistic anti-CD40 antibody to produce an optimal proliferative response of purified small dense B cells. Furthermore, 4F11 antibody synergizes with suboptimal amounts of 1C10 antibody to rescue B lymphoma cells from anti-IgM-induced growth arrest. The 1C10 and 4F11 antibodies were unable to cross-block each other's binding to recombinant CD40 expressed in L cells, providing strong support for the notion that the antibodies recognize distinct epitopes on CD40. The potential implications of two functionally distinct CD40 epitopes are discussed.
authors.affiliation: DNAX Research Institute, Palo Alto, CA 94304.
authors.forename: A W
authors.initials: AW
authors.lastname: Heath
authors.forename: W W
authors.initials: WW
authors.lastname: Wu
authors.forename: M C
authors.initials: MC
authors.lastname: Howard
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D016525:Antigenic Modulation / Q000276:immunology; D015703:Antigens, CD / Q000276:immunology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D019013:CD40 Antigens; D002455:Cell Division / Q000276:immunology; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology*; D005260:Female; D005455:Fluorescent Antibody Technique; D051379:Mice; D008807:Mice, Inbred BALB C; D011233:Precipitin Tests; D051381:Rats; D011917:Rats, Inbred Lew; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D019013:CD40 Antigens; D000939:Epitopes