IFN-α response of IPCs to CpG after in vitro or in vivo treatment with mAb 440c. (A) In vitro cross-linking of IPCs with mAb 440c blocks IFN-α secretion. IPCs were sorted from the spleen and cultured with CpG 2216 ODN on plates coated with mAb 440c or control rat IgG2b. After 24 hours, IFN-α was measured in culture supernatants by ELISA. Representative data of one of 3 separate experiments are shown. (B) In vivo treatment of mice with mAb 440c reduces serum levels of IFN-α. 129/SvJ mice were simultaneously treated subcutaneously with CpG 2216 ODN or PBS and intraperitoneally with mAb 440c or control rat IgG2b. After 16 hours, serum levels of IFN-α were detected by ELISA. Results are expressed as the mean of 3 mice per group with standard deviation indicated. Representative data of one of 3 independent experiment are shown. (C) In vivo treatment with mAb 440c does not deplete IPCs. 129/SvJ mice were treated with 2 intraperitoneal injections each of 200 μg mAb 440c at a 24-hour interval. Splenocytes were isolated 24 hours after the last injection and subjected to flow cytometric analysis. Plots show expression of Gr-1 and CD11b on gated CD11c⁺ cells. The percent of CD11c⁺/Gr-1⁺/CD11b-IPCs is indicated. Results are representative of 3 separate experiments.