Functional analysis of GAT-specific T cell clones: H-2-restricted monoclonal T helper cells do not regulate expression of antibody isotypes.

We obtained T cell clones specific for poly (Glu60, Ala30, Tyr10) (GAT) from GAT-primed lymph node cells of BALB/c mice. The clones consisted of helper cells that were carrier-specific and H-2-restricted and required a hapten-carrier bridge to activate B cells. They may be considered TH1 cells. They could all induce antibody responses of various isotypes in adoptive transfer in vitro. Isotypic patterns of the responses obtained with the clones were identical to those obtained with polyclonal T cells and were not dependent on the number of T helper cells added to the culture. Therefore, our observations demonstrate that classic TH1 cells do not regulate isotype expression on secondary responses. The expression of idiotype-like determinants on the GAT-specific clones was assayed. A syngeneic anti-idiotypic serum (B658), prepared in BALB/c mice against BALB/c anti-GAT antibodies previously characterized, was shown to block specifically the helper activity of GAT-specific T cell lines from BALB/c mice. Under the same experimental conditions the activity of none of the BALB/c clones was affected by serum B658.