FIG. 4.

X4 but not R5 strains induce extensive apoptosis in bystander CD4 T cells. Human lymphoid cultures ex vivo were infected for 7 days with the R5 strain 1/85 or 49-5, the R5X4 strain 7/86, the X4 strain NL4-3, or kept uninfected. Apoptosis in productively infected and uninfected CD4 T cells was determined by either annexin V staining (A and C) or caspase-3 activity (B). Intracellular p24 (A and B) or viral RNA (C) was used to determine viral infection. Error bars indicate standard errors of the means.