γδ T Cells promote anterior chamber-associated immune deviation and immune privilege through their production of IL-10

Anterior chamber-associated immune deviation (ACAID) is a form of peripheral tolerance that is induced by introducing Ags into the anterior chamber (AC) of the eye, and is maintained by Ag-specific regulatory T cells (Tregs). ACAID regulates harmful immune responses that can lead to irreparable injury to innocent bystander cells that are incapable of regeneration. This form of immune privilege in the eye is mediated through Tregs and is a product of complex cellular interactions. These involve F4/80(+) ocular APCs, B cells, NKT cells, CD4(+)CD25(+) Tregs, and CD8(+) Tregs. gamma delta T cells are crucial for the generation of ACAID and for corneal allograft survival. However, the functions of gamma delta T cells in ACAID are unknown. Several hypotheses were proposed for determining the functions of gamma delta T cells in ACAID. The results indicate that gamma delta T cells do not cause direct suppression of delayed-type hypersensitivity nor do they act as tolerogenic APCs. In contrast, gamma delta T cells were shown to secrete IL-10 and facilitate the generation of ACAID Tregs. Moreover, the contribution of gamma delta T cells ACAID generation could be replaced by adding exogenous recombinant mouse IL-10 to ACAID spleen cell cultures lacking gamma delta T cells.