IL-7 enhances T-cell stimulation by DCs to induce LIP. (A) T cells from F5 Rag1^−/− donors were transferred (2 × 10⁶ /mouse) to Rag1^−/−, β2m^−/−Rag1^−/−, or Il7^−/−Rag1^−/− hosts (n = 5/group). At various days, spleens were taken from recipient mice and stained for CD8, TCR, and CD5. Histograms of CD5 expression 7 days after transfer of F5 T cells to Rag1^−/− hosts (solid line) and Il7^−/−Rag1^−/− (broken line) hosts compared with expression by F5 T cells from control F5 Rag1^−/− mice (gray fill). Histograms of CD8 expression are of F5 T cells 7 days after transfer to Rag1^−/− hosts (solid line), β2m^−/−Rag1^−/− hosts (gray fill), and Il7^−/−Rag1^−/− hosts (broken line). Graph shows CD5 expression after transfer to Rag1^−/− (solid) or Il7^−/−Rag1^−/− hosts (empty) as percentage of expression by F5 T cells from control mice. (B) F5 T cells were CFSE-labeled and transferred (2 × 10⁶ cells/mouse) to Rag1^−/− and Il7^−/−Rag1^−/− hosts. At days 7, 14, and 21, lymphocytes were recovered and stained for expression of CD8 and TCR. Histograms are of representative CFSE profiles at day 14 and indicate gates used to examine cells that had undergone different number of division. Line graphs show TCR expression by F5 T cells that have undergone different numbers of divisions at day 7 (□), day 14 (), and day 21 (■) after transfer into the hosts indicated normalized to expression in control F5 Rag1^−/− mice.