Abstract
Spleen cells from a LEW.AVN rat immunized with cells from an MNR rat were fused with mouse myeloma cells to produce hybrid cell lines. One of these hybridomas produced a monoclonal antibody that was cytotoxic for bone marrow-derived (B) but not thymus-derived (T) cells. The antigen defined by this antibody is determined by a gene linked to the major histocompatibility complex (MHC). The antigen is also present on B cells of most mouse strains and is determined by an MHC-linked gene in this species as well. In both rats and mice, the gene determining the antigen maps within the immune response region of the MHC. All human B-cell lines, but not T-cell lines, and B but not T cells of all human donors tested so far are also positive for this antigen. Among human-mouse somatic cell lines that have lost various human chromosomes, this B-cell antigen is present on all lines that are positive for HLA antigen but is absent from all lines that have lost HLA.