Ir gene expression on T cells: effect of a monoclonal antibody directed against I region-controlled determinants on T cells.

A monoclonal antibody directed at an I region-controlled epitope uniquely expressed on T cells (Iat) was studied for its in vivo effect on the antibody response under the control of an Ir gene. The antibody was produced by a hybridoma made from A.TH spleen cells immune to A.TL (anti-Ik), that was selected for its reactivity with T but not B cells and macrophages, and thus was designated as anti-IatK. The injection of this anti-Iatk into H-2k, H-2b and H-2k X bF1 mice resulted in the suppression of antibody response to poly-L-(His,Glu)-poly-D,L-Ala--poly-L-Lys [(H,G)-A--L] in H-2k and F1 mice but not that to poly-L-(Tyr,Glu)-poly-D,L-Ala--poly-L-Lys [(T,G)-A--L] both in H-2b and F1 mice. The adoptive cell transfer of the combinations of anti-Iatk- or normal mouse serum-treated T and B cells into irradiated hosts demonstrated that anti-Iatk primarily affected (H,G)-A--L-specific helper T cells but not B cells and macrophages, resulting in the specific elimination of the antibody response. Suppressor T cells were not induced by the treatment with anti-Iatk. The antibody specifically eliminated the (H,G)-A--L-specific but not (T,G)-A--L-specific helper T cells in F1 spleen cells that had been primed with both (H,G)-A--L and (T,G)-A--L. The results indicated that anti-Iatk affected the H-2k-associated Ir gene function born by T cells but not by antigen-presenting cells, which was expressed on F1 helper T cells with apparent exclusion of the other allele, and implied that the Iat antigen on helper T cells is one of the sites of expression of Ir genes.