The majority of thymocytes with a high level of IL-3R are thymic DC precursors. Total thymocytes were stained for three-color FACS analysis with anti-IL–3RPE, anti-CD4 Tricolor and either anti-CD1 FITC or anti-CD45RA FITC. The histograms show the staining of CD1a and CD45RA of CD4⁺ IL-3R^high cells as gated in the dot plot (0.1% of total thymocytes).