Fine specificity of a T cell line reactive to bovine insulin.

A continuous T cell line was established from lymph node T cells of (high responder X low responder) hybrid mice ((B10 X B10.BR)F1) immune to bovine insulin (BI). T cells were expanded by restimulation with BI presented on irradiated syngeneic spleen cells and by culture in interleukin 2-containing medium. The proliferative response, measured in a 3H-thymidine incorporation assay, was specific for the selecting antigen BI; unrelated proteins did not induce DNA synthesis. However, in addition to BI the T blasts were efficiently restimulated by pig and sheep insulin, which are identical to BI except for the amino acid sequence in the A chain loop. This suggests that the T blasts recognized an antigenic determinant(s) different from the A chain loop epitope of BI, the essential antigenic moiety for cells of high responder parental H-2b mice. Induction of the blasts to DNA synthesis by the three insulins required the presence of F1 spleen cells. Parental strain B10 or B10.BR splenocytes failed to support a proliferative response, even when present as a mixture. The antigen-presenting determinants unique to F1 cells were mapped to the I-Ab/Kb and I-Ak loci. These data demonstrate that, although at least the majority of responding T cells in H-2b high responder mice recognize the A chain loop determinant of BI in the context of restriction elements of the b haplotype, T cells can be isolated from (high responder X low responder)F1 mice, which require recognition of other determinants on the insulin molecule in the context of F1 unique restriction structures for stimulation to occur.