Time course of CD95 expression for CD4⁺, CD8⁺, and CD56⁺ lymphocytes after EBV infection. PBMCs were incubated on ice for 2 hours with 1/10 vol of concentrated B95-8 virus (▪) or mock virus (•) preparations, washed with PBS, and cultured at 5 × 10⁵ cells/mL in 2 mL of culture medium. Aliquots were taken at hourly intervals and stained by 2-color immunofluorescence using FITC-conjugated CD95 and PE-conjugated anti-CD4 (A), anti-CD8 (B), or anti-CD56 (C) MoAbs. (D) PBMCs from 4 different blood donors were stained at 24 hours for CD95 (□), for CD95 and CD56 (▤), for CD95 and CD4 (▩), or for CD95 and CD8 (▪). Results are expressed as the mean percentage positive ± SEM. CD95-fluorescence activity found in untreated cells (medium only) was subtracted from both mock- and virus-treated samples before plotting for each time point.