IL-21 decreases antigen-specific IgE production in immunized mice.

(A) BALB/c mice were immunized intraperitoneally twice with (▪) or without (■) OVA at a 2-week interval. The mice were injected intraperitoneally with IL-21 (0.5 μg/mouse) twice a week for 4 weeks, with the first injection of IL-21 being done at 4 hours before the first immunization with OVA. As a control, the mice were injected intraperitoneally with PBS. Two weeks after the second immunization, the sera were collected and antigen-specific IgE, IgG1, and IgG2a were evaluated. Data are means ± SD for 7 mice in each group. Single and double asterisks indicate significantly different from the mean value of the corresponding response in the control mice,P < .005 and P < .01, respectively. (B) IL-21 decreases antigen-induced eosinophil recruitment into the airways. BALB/c mice were immunized with OVA and injected with IL-21 or PBS (as a control) as described above. Two weeks after the second immunization, mice were challenged with the inhaled OVA (▪) or saline (■). In IL-21–injected mice, IL-21 (0.5 μg/mouse) was also administered at 2 hours before and 22 hours after the inhaled OVA challenge. The number of eosinophils, lymphocytes, and macrophages in the bronchoalveolar lavage fluid was evaluated at 36 hours after the inhaled OVA challenge. Data are means ± SD for 5 mice in each group. Asterisk indicates significantly different from the mean value of the corresponding response in the control mice,P < .01.