Limited diversity of T-cell receptor γ-chain expression of murine Thy-1⁺ dendritic epidermal cells revealed by V(γ)3-specific monoclonal antibody

To study the origin of and the degree of T-cell antigen receptor (TCR) diversity of Thy-1⁺ dendritic epidermal cells (Thy-1⁺ dECs) in mice, we have developed a monoclonal antibody (mAb 536) to the γδ TCR. mAb 536 binds to and stimulates interleukin 2 secretion from Thy-1⁺ dEC but not cells that express TCR composed of α and β chains. mAb 536 precipitates CD3-associated γ and δ chains from lysates of radioiodinated Thy-1⁺ dECs. Analysis of a panel of hybridomas that express γδ TCR indicated that mAb 536 defines an epitope of the variable region (V(γ)3) gene product. Flow cytometric analysis revealed that expression of V(γ)3 in the adult mouse is restricted to cells in the epidermis, where essentially all Thy-1⁺ cells are V(γ)3⁺. The majority of CD3⁺ cells in the 14-day fetal thymus also express V(γ)3. These results indicate that the T-cell complement in epidermis are cells that express γδ TCR and that the diversity of antigens recognized by the cells might be restricted by the use of a single V(γ) gene segment. Finally, the data raise the intriguing possibility that Thy-1⁺ dECs may arise from precursors that are among the first to emerge from the developing thymus. This suggests that V gene usage during thymocyte development is highly regulated and has important consequences on the tissue localization and function of the emerging cells. As in other developing tissues, it appears that programmed and transient gene expression determines the fate of the emerging cells.