Thymi generated on reversion of the Foxn1 R allele in <i>R/−; CreERt2</i> mice support normal T cell development.

<p>Thymi from 6 week old C57BL/6 wild type, and <i>R/− reERt2</i> mice injected with 4OHT at the doses shown were dissected. Thymocytes were collected and processed for flow cytometric analysis. Plots show staining with the markers shown after gating out dead cells and on CD45⁺ cells. (<b>A</b>) Thymi from mice injected with carrier-only contained no CD4⁺ CD8⁺ DP cells (percentage of DP cells: Carrier-only injected, 0.0125±0.015 n = 4; Wild-type, 85.96±1.74 n = 7), while thymi from 1.5 mg 4OHT injected mice contained DP and SP cells. (<b>B</b>) Plots show staining with CD44 and CD25 after gating against a lineage cocktail (lin). (lin = CD3, CD4, CD8, NK1.1, Ter119, CD19, Mac1). Thymic rudiments from carrier-injected mice contained no DN2, DN3 or DN4 thymocytes. The CD45⁺ cells in the DN1 gate most likely represent circulating CD45⁺ cells present in the tissue dissected along with the thymic rudiment, as no CD45⁺ cells were observed within the epithelial component of the rudiment itself; it is possible that these cells might be hematopoietic progenitors attracted by the undifferentiated TEC but not licenced to colonise the epithelial rudiment itself. Thymi from 1.5 mg 4OHT injected <i>R/−; CreERt2</i> mice contained all normal DN populations. n>3 for WT and carrier-injected; n = 1 for 1.5 mg (equivalent data were obtained from mice injected with 0.5 mg [n = 3] and 1.0 mg 4OHT [n = 3]).