H-2 restriction as a consequence of intentional priming: T cells of fully allogeneic chimeric mice as well as of normal mice respond to foreign antigens in the context of H-2 determinants not encountered on thymic epithelial cells.

Fully allogeneic chimeras were able to develop in vitro alloantigen-specific, as well as H-2-restricted, Sendai virus-specific cytotoxic T-lymphocyte (CTL) response. Depending on the immunization regimen used, Sendai virus-specific CTL responses were restricted to the H-2 antigens of either the stem cell donor or the thymus. Similarly, unprimed splenic T cells of normal mice were found to contain CTL-precursor cells that specifically reacted against Sendai virus or trinitrophenyl derivatives in the context of allogeneic major histocompatibility complex determinants that had not been encountered during their thymic differentiation. A frequency analysis of allogeneically versus syngeneically restricted virus-specific CTL precursors present in splenic T cells showed a ratio of about 1 to 6. These results provide evidence that H-2 restriction of trinitrophenyl- or Sendai virus-specific T cells is dictated by the complex type of the antigen-presenting cell and thus appears to be independent of the type of thymus in which the T cells have undergone maturation.