IFN-γ expression by PBMCs from controls and XLP patients following stimulation. ELISPOT analysis was used to determine IFN-γ expression following stimulation of PBMCs from controls (C) and XLP patients (P1, P2, and P3) with (panel A) PMA, (panel B) CD3 or CD3/2B4, and (panel C) 2B4 alone or autologous LCL stimulation. Error bars indicate standard deviation.