Predominant involvement of CD8⁺CD28^- lymphocytes in human immunodeficiency virus-specific cytotoxic activity

Distinct functional CD8⁺ T-cell populations have been observed during human immunodeficiency virus (HIV) infection. One of these functions is the inhibition of viral replication by a noncytotoxic mechanism, which was shown to be mediated by the CD8⁺CD28⁺ subpopulation. On the other hand, CD8⁺ T cells exert an HIV-specific cytotoxic activity. The present study shows that CD8⁺CD28^- lymphocytes display this HIV-specific cytotoxic activity, which is detectable immediately after the cells are purified from peripheral blood. The CD28^- population is also able to proliferate and to retain its cytotoxic activity after in vitro restimulation with autologous blast cells. Finally, HIV-specific cytotoxic T cells can be obtained in vitro from the CD8⁺CD28⁺ population.