Suppression of human cytotoxic T lymphocyte responses by adherent peripheral blood leukocytes.

Cytotoxic T lymphocyte (CTL) responses to HLA alloantigens are unexpectedly weak compared to the CTL response to influenza virus. Allogeneic CTL activity was increased dramatically by removal of a Leu M3+ cell with adherence properties. The Leu M3+-enriched population was capable of suppressing the allogeneic-CTL response. Precultured cells suppressed both allogeneic and influenza-specific CTL responses. Inactivation of suppression was achieved by addition of influenza virus to the cultures in which suppressor activity was generated. A high proportion of asymptomatic HIV-seropositive and AIDS patients, as well as one high-risk group appear to have lost suppressor-cell activity. These findings are discussed with respect to the possible role of this suppressor system in transplantation immunology and the T cell-immune abnormalities observed in development of AIDS.