Expression of Tac antigen on human immature B-cell lineage leukemic cells.

Expression of interleukin 2 (IL-2) receptor (Tac antigen) on leukemic cells from 4 patients with acute lymphocytic leukemia (ALL) and 3 patients with blastic crisis of chronic myelogenous leukemia (CML-BC) was examined. Cells from 6 out of 7 patients did not carry immunoglobulins on their surfaces, but reacted with monoclonal antibodies (mAb) detecting B-cell related antigens such as B1, OKB2 and Leu12. Cells from two cases expressed Tac antigen immediately after cell separation. Phorbol 12-myristate 13-acetate (PMA) could induce Tac antigen in all cases. SDS-PAGE analysis of immunoprecipitates by anti-Tac mAb demonstrated that the molecular weight of Tac antigen on most of the leukemic cells was similar to that of Tac antigen present on Con A-stimulated normal lymphocytes. These leukemic cells poorly responded to exogenous recombinant IL-2. These findings suggest that IL-2 may interact with the immature and mature B cells, and play an important role in the differentiation of B lymphocytes.