Generation and characterization of monoclonal antibodies reactive with human B lymphocytes.

Four novel monoclonal antibodies directed at determinants on human B lymphocytes were produced and characterized by flow cytometry using indirect immunofluorescence analysis. The antibodies, OKB1, OKB2, OKB4, and OKB7, define antigens not previously described on human B lymphocytes using B cell reactive monoclonal antibodies or standard B cell phenotypic markers. OKB4 [immunoglobulin M (IgM)] and OKB7 (IgG2a) were reactive with greater than 95% of all surface membrane immunoglobulin positive (Smlg+) lymphocytes and were restricted to the B cell lineage. OKB2 (IgG1) likewise reacted with greater than 95% of all Smlg+ lymphocytes; however, the antigen was also expressed on all granulocytes. In contrast to OKB2, OKB4, and OKB7, OKB1 reacted with a variable percentage of normal peripheral B cells (approximately 70 to 95%). Functional studies employing polyclonally activated B cells in a pokeweed mitogen (PWM) driven system and the reverse hemolytic plaque assay for the quantitation of Ig secreting plasma cells demonstrated that OKB1 and OKB2 inhibited the generation of plaque-forming cells (PFC) when added to cultures at day 0. OKB4 had a marginal inhibitory effect, whereas OKB7 consistently enhanced the PFC response. Immunoprecipitation studies with OKB1, OKB4, and OKB7 demonstrated that these antibodies precipitated antigens of approximately 168,000, 87,000, and 175,000 m.w., respectively. The OKB2 antigen is presently under study.