Homogeneous epithelial gamma delta T cell repertoire of the skin is shaped through peripheral selection

In contrast to the T cell receptor (TCR) diversity of major alpha beta T cells in lymphoid tissues, epithelial T cells of the murine skin, called dendritic epidermal T cells (DETC), express exclusively an invariant gamma delta TCR. Fetal thymic precursors of DETC immigrate to the skin before birth, and in adult mice T cells expressing the canonical gamma delta TCR identical to that of DETC are not found in other lymphoid or epithelial tissues. Here, we show that DETC precursors migrate to the gut as well as to the skin during fetal periods, but preferentially survive and expand in the skin after birth. We propose that similar to the thymic selection of the diverse alpha beta T cell repertoire, 'peripheral selection' of the homogeneous epithelial gamma delta T cell repertoire may be mediated by TCR signaling upon the recognition of the self-ligand, because the ligand for the DETC TCR was expressed only in the skin.