First wave fetal thymocytes expressing V3J gamma 1C gamma 1-V delta 1J delta 2C delta T cell receptors are not required for alpha beta T cell receptor rearrangement and expression.

We have determined the fetal expression of V gamma 3, delta and beta TcRs in mice transgenic for the V gamma 1.1J4C gamma 4 TcR chain. The first wave thymocytes appearing at day 14 and disappearing by day 17 in normal mice was absent from the transgenic mice. However, both mice had an almost identical number of gamma delta-bearing thymocytes throughout gestation. Therefore, it is most likely that the V gamma 3J gamma 1C gamma 1 chain was replaced in the transgenic mice by the V gamma 1.1J gamma 4C gamma 4 transgene. The appearance, although slightly earlier for the transgenic mice, of alpha beta-bearing thymocytes was also very similar between transgenic and control mice during gestation. These data suggest that whatever the role of the first wave thymocytes expressing V3-V delta 1 TcRs is, it most likely is not required for the rearrangement, expression and maturation of the alpha beta TcR repertoire. We are currently analyzing a series of gamma delta transgenic mice to determine whether other restricted populations of gamma delta-bearing T cells are involved in specific aspects of immune development or function.