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

Abstract

The antibody response of (H‐2^b × H‐2^k)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 K^b, I‐A^b and K^k, I‐A^k 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 × B10.BR)F₁ origin the complementation data could be confirmed by mapping the Ia restriction elements to K^b, I‐A^b and I‐A^k. 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‐A^b × A^k)F₁ hybrid Ia complex. I‐A^b‐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 × 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 × B10)F₁ hybrids, regardless of their sex, could present PI as well as beef, sheep and horse insulin to the F₁‐restricted ST2 cells.