CD4 and cancer: While the Fas/FasL pathway appears to participate in inducing apoptosis of CD4+ T cells in HIV (Badley et al, 1998) and of CD8+ T cells in cancer (Saito et al, 2000; Dworacki et al, 2001; Hoffmann et al, 2002), it is clearly not the only mechanism responsible for elimination of activated T cells.