Interleukin 2 receptor expression by activated HNK-1⁺ granular lymphocytes: A requirement for their proliferation

A subpopulation of HNK-1⁺ cell was found to express interleukin 2 receptor (IL 2R) as monitored by the anti-Tac monoclonal antibody after lectin or allogeneic cell stimulation. When blood mononuclear cells were stimulated with phytohemagglutinin (PHA) or concanavalin A for 3 days, or with pokeweed mitogen or allogeneic mononuclear cells for 6 days, virtually all of the HNK-1⁺ cells remained as small resting lymphocytes. One-fourth of these HNK-1⁺ cells expressed IL 2R, however, usually within 18 hr after stimulation. Neither circulating HNK-1⁺ cells nor unstimulated HNK-1⁺ cells in short-term culture expressed IL 2R. Only the subset of HNK-1⁺ cells that expressed T cell surface markers, such as the sheep erythrocyte receptor and Leu-4 antigen, could be induced to express IL 2R. When long-term cultures of HNK-1⁺ cells were established with initial PHA stimulation and the continued presence of IL 2, a majority of the cells was found to express the IL 2R. When anti-Tac antibody was added to the long-term cultures, proliferation of the HNK-1⁺ cells was completely inhibited. These results suggest that entry into growth cycle by this subpopulation of HNK-1⁺ granular lymphocytes may require two signals: a relatively nonspecific ligand interaction with cell surface glycoprotein(s) to induce expression of IL 2R, and subsequent IL 2 interaction with these specific cell surface receptors.