FIG. 6.

Superantigen-induced T-cell proliferation. Resting human peripheral blood lymphoid cells alone, in the presence of autologous macrophages alone, or in the presence of SEA alone do not proliferate, as measured by [³H]-thymidine incorporation during the last 8 h of a 3-day incubation (bottom three bars). SEA exposure in the presence of MHC class II present on macrophages induces strong proliferation (top bar). HIV-1 produced from MHC class II-expressing cells was able to support the superantigen-triggered proliferative response when present as the only source of class II in the culture, and AT-2 inactivated virus was as active as untreated HIV-1. Formalin or heat treatment of HIV-1 rendered virions incapable of supporting superantigen-induced proliferative responses. Representative results from one of three experiments are shown; each bar represents the mean of triplicate cultures ±1 standard error of the mean.