Fig 2: Endogenous type I IFN signaling regulates the production of antigen-specific IgG subtypes induced by mBSA plus IFA. Wild-type mice and mice unable to express functional type I receptor (IFNARKO) were immunized with mBSA plus IFA twice in a 1-week interval followed by intraarticular injection of mBSA in PBS 21 days later. Serum was collected at days 0, 14, 21, and 28 and analyzed for mBSA-specific antibodies with ELISA by using detection antibodies specific for (A) IgG1, (B) IgG2a, and (C) IgG2b. Data are expressed as the mean absorbance (450 nm) ± SEM; n ≥ 10. (*P < 0.05; **P < 0.01; ***P < 0.001; and ****P < 0.0001).

Fig 3: No effect of IFN-α on antigen-specific IgA or IgE levels induced by mBSA plus IFA. Mice were immunized twice with mBSA plus IFA with or without 1,000 U IFN-α in 1-week intervals followed by intraarticular injection of mBSA in PBS 21 days later. Serum was collected at days 0, 14, 21, and 28 and analyzed for mBSA-specific antibodies with ELISA by using detection antibodies specific for (A) IgA and (B) IgE. Black bars represent the control group without IFN-α treatment, and blue bars represent the IFN-α-treated group. Data are expressed as the mean absorbance (450 nm) ± SEM; n ≥ 12 (pooled data of two independent experiments).

Fig 4: IFN-α downmodulates initial activation and subsequent antigen-induced reactivation of proinflammatory cytokines but enhances the initial activation and prevents subsequent antigen-induced inhibition of TGF-β reactivation. Mice were immunized twice with mBSA plus IFA with or without IFN-α at 1-week intervals followed by intraarticular injection of mBSA in PBS 21 days later. Levels of IL-1β, IL-6, IL-12, IL-17, TNF, IFN-γ, IL-10, and IL-13 were determined by Luminex, and TGF-β, by ELISA in serum collected at days 0, 14, 21, and 28 during the course of AIA. Data are expressed as mean pg/ml ± SEM (n ≥ 6). The black line, blue line, and red line represent groups receiving 0 U, 1,000 U, and 5,000 U of IFN-α, respectively, at the time of mBSA immunizations. Mann–Whitney U test was performed to compare cytokine levels between two groups. Animals not receiving intraarticular injection of mBSA (the dotted line) produced significantly (P < 0.05) less of all analyzed cytokines at day 28 compared with the control group. *P < 0.05 between PBS (black) and IFN-α 1,000 U (blue). #P < 0.05 between PBS (black) and IFN-α 5,000 U (red). The experiment was performed twice with similar results.