Inhibition of apoptosis in anti-CD3–stimulated 3DO cells by soluble anti-Fas MoAb. In one experiment representative of three, anti-CD3–stimulated cells (10 μg/well) were cultured in the presence of soluble anti-Fas or control MoAbs. Apoptosis was evaluated by flow cytometric analysis of PI-stained nuclei after 20 hours of culture.