Effects of anti-Tac antibody on the response of large granular lymphocytes to interleukin-2.

Large granular lymphocytes (LGL), which consist of a unique population comprising almost all of the natural killer (NK) cell activity, were separated from peripheral blood mononuclear cells by sequential depletion of monocytes and conventional discontinuous Percoll density gradient sedimentation. The LGL populations thus obtained exhibited significant levels of interferon-gamma (IFN-gamma) production and proliferation, as well as augmentation of NK cell activity in response to interleukin-2 (IL-2). Among these IL-2-driven phenomena, only IFN-gamma production was markedly inhibited by the monoclonal anti-Tac antibody, which presumably recognized the IL-2 receptor, whereas the proliferative response and the augmentation of NK cell activity were only minimally affected by the same antibody, even at the higher concentration. The dissociation of the effects of anti-Tac antibody on these IL-2-driven events gives us some insight on the role of IL-2 receptors involved in these immunologically interesting functions of IL-2.