Activation of leukemic large granular lymphocytes by interleukin-2 via the p75 interleukin-2 receptor.

We studied the role of interleukin-2 (IL-2) receptor subunits in the activation of leukemic CD3+ large granular lymphocytes (LGL). Peripheral blood mononuclear cells from four patients with CD3+ LGL leukemia were activated with 500 mu/ml of recombinant IL-2. Induction of both proliferative and cytotoxic functions by IL-2 was blocked by addition of anti-p75 IL-2 receptor monoclonal antibody, but not by addition of anti-p55 IL-2 receptor monoclonal antibody. Sorting experiments demonstrated directly that the effects of the anti-p75 IL-2 receptor monoclonal antibody were on leukemic LGL. These results show constitutive expression of functional p75 IL-2 receptors on leukemic LGL and suggest a possible mechanism for leukemic LGL proliferation in vivo.