E64d does not inhibit apoptosis induced directly via Fas. Fresh PBL from uninfected (n = 3) or HIV⁺ (n = 4) individuals were treated with anti-Fas antibody CH11 (100 ng/mL) in the presence or absence of 50 μmol/L E64d. Cell viability was determined in duplicate wells by trypan blue exclusion after 20 hours of culture. (B) The PBL used in (A) were cultured in complete medium for 3 days in the presence or absence of 50 μmol/L E64d. Cell viability was determined in duplicate wells by trypan blue exclusion.