Comparative differentiation kinetics of the second wave of thymocyte progenitors (E13) after intravenous injection in recipients during active (E13) or negative (E10 and E15) thymus colonization periods. Proportion of thymocytes expressing γδTCR or β(Vβ1)TCR among donor ov⁺ thymocytes was determined by immunofluorescence flow cytometry. Each point corresponds to the mean value for three to five animals in two independent experiments. The differentiation of second wave T-cell progenitors was analyzed by adoptive transfer of E13 H.B19ov⁺ BM into E10, E13, and E15 H.B19ov-embryos (injections of 10 × 10⁶cells).