γδ T-Cell Precursor-Derived CD4− CD8−αβ T Cells Retain γδ Cell Function

We have previously shown that some of the DNαβ⁺ T cells arising in TcRα-chain transgenic mice are of γδ T cell origin, based on phenotypic data and on their status of TcR gene rearrangements. In the present report we investigated the impact of αβ TcR expression on the functional programme of the mature γδ precursor-derived DNαβ⁺ T cells. Our results demonstrate that both their proliferative capacity and their cytokine production profile are similar to that of γδ T cells. Furthermore, both transgenic DNαβ⁺ T cells and DNγδ⁺ T cells up-regulate CD8α expression after activation, but, in contrast to CD4⁺αβ T cells, are unable to induce proliferation of naive B cells. Thus, our results suggest that the effector functions of mature T cells are determined independently of the TcR isotype, probably at an early stage of differentiation, and thereby have important implications for current models of T-cell lineage commitment.