J. Li, R. Reantragoon, L. Kostenko, A.J. Corbett,G. Varigos, F.R. Carbone
Mucosal-associated invariant T (MAIT) cellsare a novel subset of innate-like T cells that comprise 1–10% of human peripheral blood T cells and are enrichedin mucosal tissues. MAIT cells exhibit several characteris-tic features including expression of the semi-invariant Tcell receptor Va7.2 and restriction by the non-classicalmajor histocompatibility complex (MHC) class I-like mole-cule MR1. The presence of MAIT cells in normal and pso-riatic human skin has recently been reported, but theirexpression of skin-tropic molecules and involvement inother cutaneous pathologies has not yet been explored.
To examine the expression of skin-tropic mole-cules by MAIT cells at steady state, we performed ﬂowcytometric analysis of blood and skin samples from healthydonors. To investigate any potential wider contribution ofMAIT cells to skin disease, we examined psoriasis, alope-cia areata and dermatitis herpetiformis biopsies usingimmunoﬂuorescent staining to identify the proportion of Tcells expressing MAIT cell surface markers.
We found that MAIT cells constituted a small pop-ulation of T cells in normal human skin, similar to the per-centage found in peripheral blood. Like other skin T cells,skin MAIT cells expressed high levels of the skin-asso-ciated markers cutaneous lymphocyte antigen and CD103.Interestingly, in psoriasis and alopecia areata the propor-tion of MAIT cells was similar to that found in normal skin,but in dermatitis herpetiformis the proportion of MAITcells was signiﬁcantly elevated. These results suggest thatMAIT cells may play a role in the pathogenesis of dermati-tis herpetiformis.