αβ T cells replacing dermal and epidermal γδ T cells in Tcrd-/- mice express an MHC-independent TCR repertoire.

The epidermis of mouse skin is usually populated by dendritic epidermal T cells (γδDETC) expressing an invariant Vγ5Vδ1+ TCR. In Tcrd-/- mice, skin-resident γδDETC are replaced by αβDETC carrying polyclonal αβ TCRs. Although they exhibit a dendritic morphology, αβDETC were reported to be less functional than genuine γδDETC, likely because their TCR is unable to interact with the original TCR ligands of γδDETC. However, the TCR repertoire of those replacement DETC in Tcrd-/- mice might provide clues for understanding the development and selection of canonical γδDETC. Here, we compare the phenotype and TCR repertoires of wild-type and Tcrd-/- mouse skin T cells. Our data reveal that αβDETC are CD4/CD8 double negative and express an MHC-independent TCR repertoire. Furthermore, we identify a second MHC-independent population of CD103hi CD4/ CD8 double-negative αβ T cells in the dermis of Tcrd-/- mice.