ONTOGENY AND THYMUS-DEPENDENCE OF T-CELL SURFACE-ANTIGENS IN XENOPUS - FLOW CYTOMETRIC STUDIES ON MONOCLONAL ANTIBODY-STAINED THYMUS AND SPLEEN

Recently generated anti-Xenopus T cell monoclonal antibodies (mAbs) to the 120 kDA XTLA-1 determinant and against the putative CD5 and CD8 h omologues, together with anti-IgM and anti-MHC class II mAbs, are used in dual colour how cytometric experiments to characterize cell surfac e antigenic expression on lymphocytes in thymus and spleen of Xenopus laevis during larval and early adult life and also in metamorphosis-in hibited animals. Histological confirmation of T cell emergence early i n larval ontogeny is supplied by cryostat sections stained for CD8. Fi ve-day thymectomy, i.e. prior to T-lineage cell differentiation in the thymus, abolishes T cell marker expression in the spleen for up to 1 year. Moreover, late larval (20 days) or early adult (3 months) thymec tomy (i.e. removal after peripheralization of T cells has occurred) al so leads to severe depletion of mAb-dedned T cells in the spleen.