Figure 1.

Interleukin-21 (IL-21) depletion increases CD4 T-cell responses to primary respiratory syncytial virus (RSV) challenge. Mice were challenged with RSV on d0 and treated with αIL-21 antibody (0.5 mg; intraperitoneally; Dep) or isotype control (Con) 1 day before and after challenge. (a) Mice were weighed daily, and percentage of weight loss was calculated. Lungs were harvested, processed, and RNA extracted as described in Materials and Methods. cDNA was produced by real-time reverse transcriptase–PCR and copies of the RSV L gene were determined by quantitative PCR (Taqman). Plasmids encoding the L gene were used as standards to quantitate L gene copies. (b) Results are expressed as the number of L gene copies. Bronchoalveolar lavage (BAL) fluid and lungs were harvested at d7 post challenge. CD4 T cell, CD8 T cell, and natural killer (NK) cell recruitment into (c) BAL fluid and (d) their ICOS (inducible costimulatory molecule) expression was determined by flow cytometry. (e) Cytokines were quantitated in BAL fluid by sandwich enzyme-linked immunosorbent assay. (f) Interferon (IFN)-γ production by lung CD4 and CD8 T cells was determined by flow cytometry. Error bars represent s.e.m. The graphs are representative of three independent experiments of five mice per group. Student's t-test result; *P<0.05, **P<0.01, ***P<0.001. RANTES, regulated and normal T cell expressed and secreted; TNF, tumor necrosis factor.