Phenotypic analysis of cells recovered from FTOC treated with IL-7. Cells were recovered from fetal thymic lobes after 12 days of culture, and triple-labeled for flow cytometry analysis as described in Materials and Methods. CD4 versus CD8 expression is represented in the dot plots with percentages of cells included in the corner of each quadrant. The cells within each quadrant were also examined for expression of CD3. The percentages in the corner of each histogram represent the proportion of cells expressing high levels of CD3. The profiles shown are representative of six independent experiments.