Epitope specificity and Ia restriction of T cell responses to insulin in a system of complementing Ir genes: analysis with primed lymph node T cells and a long-term cultured T cell line.

The antibody response of (H-2b X H-2k)F1 mice to pig insulin (PI) has previously been shown to be under the control of H-2-linked, complementing Ir genes. In addition, this response was reported to depend on the genetic background of the parental strains (Keck, K., Eur. J. Immunol. 1977. 7: 811). Here it is demonstrated that the secondary in vitro response of proliferating T cells shows the same dependence on H-2-linked Ir genes yet an influence of the background genes could not be detected. The complementing genes were mapped to the Kb, I-Ab and Kk, I-Ak regions. For restimulation of F1 T cells by PI, the Ir genes of both parental chromosomes have to be expressed in the same antigen-presenting cell, suggesting complementation at the molecular rather than at a cell interaction level. With a long-term cultured, PI-specific T cell line (ST2) of (B10 X B10.BR)F1 origin the complementation data could be confirmed by mapping the Ia restriction elements to Kb, I-Ab and I-Ak. The reactivity pattern of this line towards species variants of insulin and the isolated A and B polypeptide chains in the presence of syngeneic accessory cells suggests that the glutamic acid residue in position 4 of the A polypeptide chain (Asp in mouse insulin) is essential for recognition in conjunction with an (I-Ab X I-Ak)F1 hybrid Ia complex. I-Ab-encoded molecules carrying specificity Ia. W39 which, according to Rosenwasser, L. J. and Huber, B. T. are essential for the presentation of BI to (CBA/N X C57BL/6)F1 T cells, are not required as components of the F1-unique restriction element recognized by the F1 T cells of the ST2 line in conjunction with PI. This is indicated by the fact that accessory cells of (CBA/N X B10)F1 hybrids, regardless of their sex, could present PI as well as beef, sheep and horse insulin to the F1-restricted ST2 cells.