Effect of IL-6 or IFN-γ on anti-CD3–treated cells. Cells were cultured for 18 hours on anti-CD3 coated plates in the presence or absence of IL-6 (20 ng/mL), IFN-γ (200 U/mL), or IL-13 (10 ng/mL). Apoptosis (A) of PI-stained nuclei, Fas (B), and FasL (C) expression were evaluated by flow cytometric analysis after 18 hours of culture. Numbers on histograms represent the percentage of apoptotic nuclei, the value of Fas histogram median, and the percentage of FasL⁺ cells of a representative experiment calculated by Lysis II.