A new alloantigenic system on human lymphocytes.

Certain otherwise well-definedHL-Atyping sera contain extra antibodies which do not appear to be closely related to known HL-A specificites and which react in the cytotoxic test with chronic lymphaticleukemia lymphocytes but not with normal lymphocytes. Despite nonreactivity in thecytotoxic test, absorption studies show that the antigenic factors are well represented onnormal lymphocytes. Based on cross-absorption experiments using both normal andleukemic cells, followed by back-testing with the cytotoxic test against a leukemiccell panel, evidence is presented suggesting the existence of a complex, probablymultiple allelic system on human lymphoid cells which appears distinct from the, HL-Asystem, and is definable by serologic techniques.