Figure 1.

Circulating lin⁻hCD25⁺ precursors. (A) Lineage depleted BM and blood cells from hCD25 transgenic and non-transgenic mice were stained for lineage markers, hCD25, c-kit and B220. The lower panels show the expression of c-kit and B220 of electronically gated lin⁻hCD25⁺ cells. Numbers in FACS plots indicate percentages of cells within gates or quadrants. (B) Expression of pre-TCRα in circulating lin⁻hCD25⁺ cells. RT-PCR was performed on 250 CTP cells. The same amount of cDNA from hCD25⁺ DN3 cells and DN3 cells from Ptcra^−/− mice was used as positive and negative controls, respectively. One representative out of 2 independent experiments is shown. (C) Expression of surface markers on different lin⁻hCD25⁺ populations. BM CLP-1 (lin⁻hCD25⁺ckit⁺B220⁻) and CLP-2 (lin⁻hCD25⁺c-kit^−/loB220⁺) cells, blood lin⁻hCD25⁺B220⁺ cells (“B220⁺”) and CTP (lin⁻hCD25⁺B220⁻) and thymic hCD25⁺ DN1 (lin⁻CD25⁻CD44^hihCD25⁺) cells were stained for c-kit, IL-7Rα, Flt3, Sca-1, CD44 and Thy-1.1. Histograms show expression levels of the respective surface markers (blue histograms) or unstained controls (red histograms) of electronically gated populations as indicated above. One representative out of 2 independent experiments is shown.