Fas-costimulated and control-activated CD4 T cells are phenotypically different.

(A) Expression of TCR (Vα2), CD4, CD25, and CD45RB on viable CD4 T cells was determined at day 3 and of CD44, CD62L, and FasL at day 6 on Fas-costimulated (light gray open histograms) and control-activated (dark gray open histograms) cells. Black histograms: staining control. (B) Expression of Fas on naive CD4 T cells and after 3 and 6 days of activation on Fas-costimulated and on control-activated cells.