Emigration of selected subsets of {gamma}{delta}+ T cells from the adult murine thymus

Cells bearing the γδ form of the TCR make up only 1–3% of T cells in the adult murine thymus and peripheral lymphold organs. Evidence from studies of nude mice suggests that the development of at least some γδ T cells is thymus dependent; however, until now it has not been directly demonstrated that γδ cells are exported from the thymus. In this paper we have used the technique of labelling thymocytes in vivo with FITC, followed by flow cytometrlc analysis to trace cells emigrating from the thymus to the spleen. Using this approach we have been able to demonstrate for the first time that γδ T cells are exported from the adult murine thymus to the spleen. We also demonstrate that the cells emigrating to the spleen are a selected subset of γδ thymocytes being heat stable antigen positive, Thy-1+, and expressing low levels of CD44 (Pgp-1). In addition, investigation of TCR V γ ; gene usage among adult γδ+ thymocytes, recent emigrants, and spleen cells, indicated a selective emigration of γδ cells expressing certain V γ genes.