Reduction of Fas-mediated apoptosis in cultured ATL cells by I-309.

(A) ATL cells (PaBe) or Tax-immortalized control T cells (TAXI-1) were cultivated either in the presence of apoptosis-inducing monoclonal anti-Fas antibody alone (♦) or in the presence of anti-Fas and anti–I-309 antibody (▪), anti-Fas, anti–I-309 antibody, and pertussis toxin (●), or anti-Fas and isotypic control anti-IgG₁ antibody (▴) for 48 hours. Proliferation was measured by [³H]-thymidine incorporation. The reduced cell proliferation represents the relative [³H]-thymidine incorporation of untreated cells (set to 100%) minus [³H]-thymidine incorporation of antibody/PT-treated cells. Error bars reflect the SEM of 4 to 5 independent experiments. (B) ATL cells (PaBe) or HTLV-1–infected HAM/TSP cells (Mondi) were incubated in the absence or presence of anti-Fas antibody (−/+ anti-Fas) and in the absence (−ab) or presence of anti–I-309 (+a-I-309)/control anti-IgG antibody (+a-IgG). Induction of apoptosis was evaluated by annexin V staining and FACS analysis. One representative of 3 independent experiments is depicted.