IFN-γ expression by EBV–T-cell lines from controls and XLP patients following stimulation. ELISPOT analysis was used to determine IFN-γ expression following stimulation of EBV–T-cell lines from controls (CTLC) and XLP patients (CTLP1 and CTLP2) and SAP-transduced XLP patient EBV–T-cell lines (S + CTLP1, S + CTLP2) with (A) CD3/2B4, (B) 2B4 alone, or (C) autologous LCL. Error bars indicate standard deviation.