Quantitation of HLA class II antigens on B-cell lines

By quantitation of elutable immunoglobulin G in a recently described ELISA, the number of HLA class I and II molecules on B-cell lines was determined using monomorphic monoclonal antibodies. An average number of 183,000 binding sites per cell for HLA class I-, 99,000 for HLA-DR-, 63,000 for DQ- and 42,000 for DP-specific monoclonal antibodies were determined. The small amount of HLA class II molecules can in part explain the difficulties observed in HLA class II typing or in detection of class II antibodies using the lymphocytotoxicity text.