Normal T-cell priming but reduced T-cell recruitment to the airways in the absence of IL-21R signaling. DCs isolated from either C57BL/6 or IL-21R–deficient mice were cocultured with CFSE-labeled Sm2 T cells in the presence of GP_61-80 peptide. (A) After 24 hours, cells were collected and stained for the activation markers CD62L, CD25, and CD40L. (B) Proliferation was assessed by FACS analysis of CFSE-stained cells. IL-21^+/+ or IL-21^−/− TCR transgenic Sm2 CD4 cells were adoptively transferred into C57BL/6 mice. Mice were immunized with GP_61-80 peptide in alum adjuvant. After 10 days, mice were challenged intranasally on 4 consecutive days. One day after the final challenge, the (C) DLNs and (D) BALs were analyzed for the percentage of the transferred Sm2 cells (Va2⁺CD4⁺) by FACS. (E) The number of eosinophils in the BAL was determined by differential cell counts. Numbers in histograms represent geometric mean; numbers above gates represent percentage of cells in gate. (C-E) Column plots indicate averages ± SD of a representative experiment using 4 to 5 mice per group. Similar results were observed in 3 independent experiments.