Choroidal γδ T cells in protection against retinal pigment epithelium and retinal injury

γδ T cells located near the epithelial barrier are integral components of local inflammatory and innate immune responses. We have previously reported the presence of choroidal γδ T cells in a model of chronic degeneration of the retinal pigment epithelium (RPE). The goals of the current study were to further define the functions of choroidal γδ T cells and to explore the underlying mechanisms of their action. Our data demonstrate that choroidal γδ T cells are activated by RPE injury in response to NaIO3 treatment, and that they express genes that encode immunosuppressive cytokines, such as IL-4 and IL-10. γδ–T-cell–deficient mice developed profound RPE and retinal damage at doses that caused minimal effects in wild-type mice, and adoptive transfer of γδ T cells prevented sensitization. Intravitreal injection of IL-4 and IL-10 ameliorated RPE toxicity that was induced by NaIO3. Ex vivo coculture of γδ T cells with RPE explants activated the production of anti-inflammatory cytokines via an aryl hydrocarbon ...