Selective suppression of the cytotoxic T cell response to influenza virus in mice.

Mice injected with inactivated (UV light-irradiated) influenza virus produce specific antibody, become sensitized for a delayed-type hypersensitivity reaction, but do not generate specific cytotoxic T (Tc) cells. If injected 4-5 days later with infectious virus, the formation of Tc cells is suppressed by > 90%. If A strain viruses are used, the suppression observed is cross-reactive within A strain viruses but does not extend to B/LEE or to Sendai virus. Serum from mice injected with UV-irradiated virus contains antibodies which on adoptive transfer can inhibit Tc cell formation when infectious homologous virus is used to challenge the recipients. Spleen cells from the same mice, upon adoptive transfer, also inhibit (50-70%) Tc cell formation if transferred within 24 h of injection of infectious virus, and the specificity pattern observed is cross-reactive within A strains. The activity of the cells mediating suppression is destroyed by monospecific anti-Thy-1.2 antibody and complement. The immune cells require I region sharing between donor and recipient mice for their suppressor activity to be effective. (There is also a partial requirement for K, D region sharing, but the possible rejection of transferred cells is not excluded.) Dilution assays in which clonal expansion of Tc precursors is used to estimate their frequency and the presence of T helper (Th) cells indicate that suppressed mice possess Tc precursors and primed cells which, upon restimulation, act as Th cells. Furthermore, injection of irradiated Th cells with inactivated virus does not significantly reduce the ensuing suppression.