Resident Skin-specific γδ T Cells Provide Local, Nonredundant Regulation of Cutaneous Inflammation

The function of the intraepithelial lymphocyte (IEL) network of T cell receptor (TCR) gammadelta(+) (Vgamma5(+)) dendritic epidermal T cells (DETC) was evaluated by examining several mouse strains genetically deficient in gammadelta T cells (delta(-/-) mice), and in delta(-/-) mice reconstituted with DETC or with different gammadelta cell subpopulations. NOD.delta(-/-) and FVB.delta(-/-) mice spontaneously developed localized, chronic dermatitis, whereas interestingly, the commonly used C57BL/6.delta(-/-) strain did not. Genetic analyses indicated a single autosomal recessive gene controlled the dermatitis susceptibility of NOD.delta(-/-) mice. Furthermore, allergic and irritant contact dermatitis reactions were exaggerated in FVB.delta(-/-), but not in C57BL/6.delta(-/-) mice. Neither spontaneous nor augmented irritant dermatitis was observed in FVB.beta(-/-) delta(-/-) mice lacking all T cells, indicating that alphabeta T cell-mediated inflammation is the target for gammadelta-mediated down-regulation. Reconstitution studies demonstrated that both spontaneous and augmented irritant dermatitis in FVB.delta(-/-) mice were down-regulated by Vgamma5(+) DETC, but not by epidermal T cells expressing other gammadelta TCRs. This study demonstrates that functional impairment at an epithelial interface can be specifically attributed to absence of the local TCR-gammadelta(+) IEL subset and suggests that systemic inflammatory reactions may more generally be subject to substantial regulation by local IELs.