Phenotype of CD4⁻CD8⁻ cells raised after 12 days of culture in the absence (gray histograms) or presence of IL-7 (black histograms). These CD4⁻CD8⁻ cells were determined by gating on negative fluorescence of thymic cells stained with PE-conjugated anti-CD4 and anti-CD8. A minimum of 5,000 cells was analyzed for the expression of MHC class II, CD11b, CD68, OX-62, CD54, CD44, and CD25. Black lines represent the background fluorescence using isotype-matched irrelevant FITC-conjugated MoAb, or omitting the particular MoAb under study. The results are representative of a series of three independent experiments.