Induction of cell proliferation in RO and RA subsets of CD4 cells. Separate cell aliquots were taken from the experiments described in Fig. 1; and cell proliferation was measured on day 4 after stimulation with (A) PHA with (white bars) or without (striped bars) rIL-2 or (B) antiCD3 with (white bars) or without (black bars) anti-CD28, in HIV-infected cells (NL or nef) compared with uninfected cell controls (CC). Data represent the mean values of three experiments.