T cell sensitivity to TGF-β is required for the effector function but not the generation of splenic CD8(+) regulatory T cells induced via the injection of antigen into the anterior chamber

The introduction of antigen into the anterior chamber (AC) of the eye induces the production of antigen-specific splenic CD8(+) regulatory T cells (AC-SPL cells) that suppress a delayed-type hypersensitivity (DTH) reaction in immunized mice. Because the generation of these regulatory T cells is also induced by exposure to transforming growth factor (TGF)-β and antigen or F4/80(+) cells exposed to TGF-β and antigen in vitro, we investigated (i) whether these cells are produced in dominant negative receptor for transforming growth factor β receptor type II (dnTGFβRII) or Cbl-b(−/−) mice whose T cells are resistant to TGF-β, (ii) whether DTH is suppressed by wild type (WT) CD8(+) AC-SPL cells in Cbl-b(−/−) and dnTGFβRII mice and (iii) the effect of antibodies to TGF-β on the suppression of DTH by CD8(+) AC-SPL cells. DnTGFβRII immunized and Cbl-b(−/−) mice produced splenic CD8(+) regulatory cells after the intracameral injection of antigen and immunization. The suppression of a DTH reaction by CD8(+) AC-SPL cells in WT mice was blocked by the local inclusion of antibodies to TGF-β when WT splenic CD8(+) AC-SPL cells were injected into the DTH reaction site. Moreover, the DTH reaction in immunized dnTGFβRII and Cbl-b(−/−) mice was not suppressed by the transfer of WT CD8(+) AC-SPL cells to the site challenged with antigen. In aggregate, these observations suggest that T cell sensitivity to TGF-β is not an obligate requirement for the in vivo induction of CD8(+) AC-SPL T cells but the suppression of an in vivo DTH reaction by CD8(+) AC-SPL cells is dependent on TGF-β.