The objective of this research is to identify previously unrecognized genes in the HLA region, the major histocompatibility complex (MHC) of humans. The overall approach will be to isolate cell line variants with deletions in the HLA region by mutagenesis and immunoselection. These deletion variants and the progenitor cells from which they were derived will serve as target cell panels to screen for monoclonal antibodies reactive with MHC-coded antigens. The patterns of reactivity with the progenitor cells, the deletion variants and other selected variants and cell lines in conjunction with serological and immunochemical analysis will be used to distinguish known and previously unrecognized antigens coded for in the HLA region. Deletion variants will also serve to enrich for mRNAs coded for by genes in the HLA region.