Host preconditioning by CTX does not lead to increased availability of IL-7 in mice. (A) The IL-7 levels in Rag2KO mice but not CTX-treated mice lead to downregulation of IL-7Rα in adoptively transferred naïve T cells. Following the timeline depicted in the schema, splenocytes from CD45.1 mice were transferred into untreated mice (WT), CTX-treated mice, and Rag2KO mice. 16 hours later, peripheral blood and spleen samples were collected and examined for expression of IL-7Rα in transferred CD4+ and CD8+ T cells by flow cytometry. Numbers in representative histograms indicate the values of mean florescence intensity (MFI) of IL-7Rα. (B) The dynamic changes in IL-7Rα expression in donor T cells are driven by antigen encounter in CTX-conditioned mice. As shown in the schema, A20HA tumor-bearing mice were treated with CTX followed by co-transfer of HA-specific and OVA-specific CD4+ T cells. Tail blood was collected at the indicated time points and examined for IL-7Rα expression by FACS. IL-7Rα expression profiles relative to cell division in HA-specific and OVA-specific CD4+ T cells are shown in representative dot plots. Results from two independent experiments are summarized in graph at right.