Selection of gamma delta T cells with canonical T-cell antigen receptors in fetal thymus.

Two gamma delta T-cell subsets that are generated in the fetal thymus and selectively localize in epidermis and uterus-vagina-tongue epithelia exhibit remarkable homogeneity in their (T-cell) antigen receptors (TCR). In the present study, we show that cells expressing the canonical gamma delta TCR are also generated in fetal thymus organ cultures. Treatment of these cultures with anti-gamma delta TCR antibodies did not prevent gamma delta T-cell development but led to a striking increase in the frequency of noncanonical in-frame sequences. We conclude from this finding that cells expressing the canonical TCR accumulate selectively as a result of TCR-mediated positive selection in the fetal thymus.