The activation of IL-2 transcription in L3T4+ and Lyt-2+ lymphocytes during virus infection in vivo.

During infection of mice with lymphocytic choriomeningitis virus (LCMV), activation and proliferation of NK cells occurs early, followed by the activation and proliferation of CTL. To investigate the role of endogenously produced growth factors in mediating proliferation of these effector cell types, the transcription of IL-2 during infection was studied. We report that IL-2 is transcribed in vivo by mouse spleen cells during infection with LCMV. The time course of transcription corresponds to CTL activation, to the accumulation of Lyt-2+ and L3T4+ T cells in the spleen, to the incorporation of [3H]TdR by B cell-depleted spleen lymphocytes, and to production of IL-2 by these cells. At the peak of CTL activation and proliferation, both Lyt-2+ and L3T4+ populations transcribed IL-2. The results strongly support a role for IL-2 in mediating CTL proliferation during LCMV infection. Furthermore, the results demonstrate that Lyt-2+ cells can transcribe helper factors such as IL-2 in vivo, which may act to promote endogenous effector cell proliferation.