Dendritic cell intrinsic IRF4 expression regulates production of regulatory cytokines during influenza virus infection

Abstract

Abstract Lung resident dendritic cells (DCs) are a heterogeneous population with diverse roles in respiratory infection. The development and function of DC subsets are controlled by distinct transcription factors including IRF4, which regulates CD11b+ cDC2 development, migration, and function. CD11c-cre Irf4fl/fl mice (KO) with a deletion of Irf4 in DCs lack a subset (P1) of lung CD11b+ DCs while other DCs are present but lack IRF4. To test the hypothesis that DC intrinsic IRF4 regulates anti-viral responses, wild type (WT) and KO mice were infected with a sublethal dose of influenza A/PuertoRico/8/34. On days 3–8 post-infection, a novel flow cytometry scheme was used to assess numbers and functional responses of lung and mediastinal lymph node (mLN) DCs, including tissue DC subsets CD103+ and CD11b+ (P1, P2), and inflammatory monocyte-derived Ly6Chi DCs. In addition to lacking CD11b+P1 DCs, KO mice had increased numbers of lung CD103+DCs, a defect in migration of CD11b+P2 DCs to the mLN and reduced numbers of Ly6Chi DCs in the mLN. In WT mice, CD11b+P1 DCs mice produced IL-10, and CD103+DCs preferentially displayed a latent form of TGFβ (LAP) and expressed Itgb8 needed to retain surface LAP for TGFβ activation. KO CD103+DCs showed reduced expression of TGFβ-LAP and Itgb8. Thus, DC production of both IL-10 and TGFβ is deficient in infected KO mice. The reduction of regulatory cytokines is consistent with our earlier finding that infected KO mice harbor decreased numbers of Foxp3+ T regulatory and CD8+ T memory cells, yet greater numbers of effector IFNg+ influenza-specific CD8+ T cells. In sum, IRF4 differentially regulates lung DC subsets to promote regulatory cytokines, and this diversity balances the anti-viral immune response to influenza infection.