Human B-lymphocyte antigens expressed by lymphocytic and myelocytic leukemia cells. II. Detection by human anti-B-cell alloantisera

The majority of human lymphocytic and myelocytic leukemia cells express a polymorphic antigen that is found on peripheral blood B-lymphocytes and cultured lymphoblastoid B-cell lines. These B-lymphocyte antigens were detected by 34 human alloantisera that were repeatedly absorbed with pooled platelets to remove all activity against HLA antigens and T-lymphocytes. Absorption studies indicated that a common antigen was present on both B-lymphocytes and positive leukemia cells. Leukemia cells could be subdivided into two groups based on the presence of the B-lymphocyte antigen. Fourteen of 18 acute myelocytic leukemia cells, 10 of 13 acute lymphoblastic leukemia cells, 4 of 6 chronic myelocytic leukemia cells, and 2 of 2 chronic lymphocytic leukemia cells were positive. This group of leukemia cells also reacted with rabbit anti-B-cell sera raised to papain digests of spleen cell membranes. F(ab')2 fragments of the rabbit antsera were shown to specifically block the reactions of the human antisera against B-cells and leukemia cells. These results suggested that the rabbit and human anti-B-cell sera were reacting with identical molecules. This conclusion was supported by immunoprecipitation data.