STAT5 silencing enhances HIV-1 p24 Gag Ag expression in IL-2 stimulated, but not in IL-7-stimulated, CD8-depleted PBMC of HIV-positive individuals. (A) CD8-depleted PBMC from patient nos. 8 and 3 were electroporated with either control or STAT5 siRNA; 24 hours later, the cells were resuspended in a medium enriched with IL-2 and p24 Gag Ag expression was analyzed by intracellular flow cytometry after 5 days of cultivation; gray histograms: scramble control siRNA; black histograms: STAT5 siRNA (upper panels). Cells from patient no. 8, but not those from patient no. 3, showed an up-regulation of p24 Gag Ag expression after STAT5 siRNA. CD8-depleted PBMC of patient no. 2 were stimulated with IL-2 or IL-7 after transfection with either STAT5 or control siRNA. Induction of p24 Gag Ag expression was observed in cells stimulated with IL-2, but not with IL-7 after 5 days of cultivation (lower panels). (B) Selective up-regulation of p24 Gag Ag expression by STAT5 siRNA in IL-2, but not IL-7, stimulated CD8-depleted PBMC cultures established from patient nos. 1, 2, 3, 4, 6, and 8 for IL-2 and from patient nos. 1, 2, 3, 4, and 6 for IL-7. *P<.05 (t test for paired values).