Human recombinant interleukin-2 is mitogenic to human lymphocytes.

Reported herein are the results of studies demonstrating that purified recombinant human interleukin-2 (hrlL-2) is a potent mitogen for lymphocytes of healthy human donors. The specificity of the hrlL-2-induced response was defined in experiments in which mitogenicity of this T cell growth-promoting lymphokine was completely abrogated by blocking the T cell membrane receptor for IL-2 with the anti-Tac monoclonal antibody. Depletion of adherent mononuclear leukocytes markedly reduced lymphocyte reactivity to hrlL-2, but the response could be fully recovered by the addition of interleukin-1 (IL-1). Increased proliferative responses were observed using a combination of hrlL-2 and a monoclonal antibody OKT3 that defines a T cell membrane antigen. These studies demonstrate that hrlL-2, as with antigens and phytomitogens, may serve as the first signal of T cell proliferation.