Differential susceptibility of Th1 and Th2 clones to gp120-apoptosis. Th1 clones 103, 3/12, and 3/21 and Th2 clones 3/39, F37, and 2/46 were treated with 10 μg/mL gp120, an equal dose of anti-gp120 MoAb, and seeded in the presence of immobilized anti-TCR MoAb. The percentage of apoptotic cells was determined at the indicated times with TUNEL and PI staining. Data are expressed as net % gp120-apoptosis (see Materials and Methods).