The expression of idiotypic determinants on suppressor T cells is independent of T cell Igh genotype.

To investigate the role played by immunoglobulins in the display of idiotope-like determinants by T cells, we investigated whether T cells transferred to congenically athymic mice would display the idiotypes of the nude host or of the T cell donor Igh genotype. 4-Hydroxy-3-nitrophenyl hapten (NP)-specific first-order suppressor T cells (Ts1) from Ighb-bearing mice display the NPb idiotype. Mature peripheral T cells from Igh congenic mice were used for reconstitution of nude mice in acute transfers. Before analyzing the idiotypic properties of the T cells in this system, we verified, using Thy-1 congenic strains, that the suppressor T cells induced were effectively derived from the transferred T cells and not from the host. The following strains of mice were selected for these studies: C57BL/6 (Ighb), B6.Ighn, and C57BL nu/nu. The NP-specific suppressor T cells generated in C57BL nu/nu mice reconstituted with T cells derived from Igh congenic B6.Ighn donors were investigated. Suppressor T cells were induced by i.v. administration of 10(4) NP-coupled B6.Ighn adherent cells. Six days later, the spleen cells from the reconstituted nude mice were treated with anti-NPb antibodies and complement before being transferred to C57BL/6 recipients immediately prior to antigen priming. Treatment with anti-idiotypic reagents depleted suppressor cell activity, which indicates that the suppressor cells obtained from C57BL/6 mice or C57BL nu/nu mice that have been reconstituted with B6.Ighn T cells bear NPb idiotype-related determinants. The data further demonstrate that the idiotype-related determinants expressed on NP-specific Ts1 are controlled not by the Ighn genotype of the T cell donor, but by the genotype of the C57BL nu/nu (Ighb) recipient host. In agreement with these findings, we further verified that the NP-specific suppressor T cells generated in C57BL nu/nu mice reconstituted with B6.Ighn mature T cells display the operational Igh restrictions of C57BL/6 mice and not of B6.Ighn mice. These experiments demonstrate how idiotypic elements expressed on the immunoglobulins of the host influence the specificity of the antigen receptor on T cells. Normally, Ts1 from B6.Ighn mice lack the NPb idiotype-related determinants and their suppressive activity is operationally restricted by the Ighn allotype. However, mature B6.Ighn T cells selected to respond to NP in C57BL nu/nu recipients display idiotype-related determinants and restriction specificities characteristic of the C57BL (Ighb) host. Thus, the environment in which Ts1 are induced and selected affects the Ts1 repertoire. How can we account for this phenomenon?