The cytotoxic T-cell response to Ia antigens: lack of correlation between the level of specific cytotoxicity obtained in primary mixed lymphocyte reaction and the frequency of specific cytotoxic T lymphocyte.

We have investigated the cytotoxic response to allogeneic I-E and I-A antigens in bulk culture and limiting dilution experiments. A high degree of specific killing could be generated from unprimed T cells of I-E-negative strains upon stimulation with cells expressing I-E. In such conditions, cytotoxic T lymphocytes (CTL) were generated in the absence of a specific proliferative response. The frequency determinations by means of limiting dilution experiments showed that I-E-specific CTL precursors were much less frequent than the K and D specific precursors. The results suggest the existence of a population of I-E-specific CTL that failed to grow under conditions that allowed the growth of class I-specific CTL.