Antigen-specific CTL are CD28− and CD38+.

For AIM subject AI-1, EBV-specific cytotoxicity by PBMC and selected CD28+ and CD38+ T cells, cultured overnight in 600 IU/mL IL-2, was measured against autologous B-LCL. No specific cytotoxicity above background was detected with freshly isolated PBMC effector cells (data not shown and Figure 5). No EBV-specific cytotoxicity was present in a preinfection sample (left) but was detectable in a 4-hour⁵¹Cr release assay 26 days after symptoms began in total PBMC (♦) and CD38+ PBMC (▴), but not in CD28+ PBMC (▪).