alpha beta T cells replacing dermal and epidermal gamma delta T cells in Tcrd(-/-) mice express an MHC-independent TCR repertoire

The epidermis of mouse skin is usually populated by dendritic epidermal T cells (gamma delta DETC) expressing an invariant V gamma 5V delta 1(+) TCR. In Tcrd(-/-) mice, skin-resident gamma delta DETC are replaced by alpha beta DETC carrying polyclonal alpha beta TCRs. Although they exhibit a dendritic morphology, alpha beta DETC were reported to be less functional than genuine gamma delta DETC, likely because their TCR is unable to interact with the original TCR ligands of gamma delta DETC. However, the TCR repertoire of those replacement DETC in Tcrd(-/-) mice might provide clues for understanding the development and selection of canonical gamma delta DETC. Here, we compare the phenotype and TCR repertoires of wild-type and Tcrd(-/-) mouse skin T cells. Our data reveal that alpha beta DETC are CD4/CD8 double negative and express an MHC-independent TCR repertoire. Furthermore, we identify a second MHC-independent population of CD103(hi) CD4/ CD8 double-negative alpha beta T cells in the dermis of Tcrd(-/-) mice.