Phenotypic profile of cells generated in vitro from thymic progenitors. Cells cultured in vitro were pooled on different days and assessed for marker expression via flow cytometry. Black histograms represent cells stained with appropriate isotype controls and colored-line histograms correspond to different days of analysis. Early (A) and late (B) marker acquisition is shown. Expression on gated NK1.1⁺ cells is shown, except for all markers on day 4 and NK1.1 expression on different days, which were gated on the lymphocyte population. (C) Developmental kinetics of sorted thymocytes as a function of days versus the percentage of NK1.1⁺ cells expressing the given marker. Again, as described for Figure 2, the staining patterns for each marker were somewhat different but we used the percent of positive cells as a convenient means to compare and describe the staining profiles for numerous antibodies used. Data are representative of 3-5 experiments.