Comparison of hapten-specific cytotoxic and suppressor T cells by a split culture approach.

The protocols for the induction of hapten-specific suppressor T cells (Ts) and hapten-specific cytotoxic T cells (Tc) are essentially the same. Hence, to exclude or support the possibility of an apparent suppression of B-cell responsiveness by elimination of B cells due to cytotoxic cells, limiting dilution cultures were concomitantly tested for suppression of a primary B-cell response against trinitrophenol (TNP), and cytotoxic activity towards a TNP-haptenized anti-TNP IgM hybridoma. When compared with the spleen cells (SC) of untreated Balb/c mice, the frequency of Tc was found to be increased after in vivo or in vitro induction of TNP-specific Ts (via intravenous injection of TNP-haptenized lymphocytes or cocultivation of SC with haptenized lymphocytes). Despite this synchronous increase of hapten-specific Ts and Tc, the number of wells displaying both cytotoxic and suppressive activity did not exceed the number of wells that were expected to contain Ts and Tc. Hence, in the system described, hapten-specific Tc did not lyse anti-hapten antibody-producing B cells to any measurable extent, and suppression of a B-cell response by in vivo or in vitro-induced Ts was independent of cytotoxic T-cell activity.