Figure 1.

IL-2 and IFN-γ independently regulate AICD. CD4⁺ T cells were purified from pooled spleen and lymph node suspensions obtained from C57BL/6 (WT), IFN-γ^−/−, or Stat1^−/− mice (A–C), or from 3A9/+ (wild-type) and 3A9/IL-2^−/− mice (D–F). These cells were activated in vitro with anti-CD3 and anti-CD28, with the following cytokines added to the cultures: none (A and D), IL-2 (50 U/ml; B and E), or IFN-γ (10 U/ml; C and F). Activated cells were collected 3 d later, and incubated on anti-CD3 coated plates in the presence of IL-2. Apoptosis was determined by Propidium Iodide staining. The same cells were analyzed for the expression of FasL (G) and Fas (H) by staining and flow cytometry. The filled histograms in G represent resting cells and the empty histograms represent activated T cells. The filled histograms in H represent cells that were stained with an isotype-matched control antibody and the empty histograms represent cells that were stained with anti-Fas.