IRF4 and IRF8 Act in CD11c+ Cells To Regulate Terminal Differentiation of Lung Tissue Dendritic Cells

Abstract

Dendritic cells (DCs) initiate immune responses in barrier tissues including lung and skin. Conventional DC subsets, CD11b− (cDC1s) or CD11b+ (cDC2s), arise via distinct networks of transcription factors involving IRF4 and IRF8 and are specialized for unique functional responses. Using mice in which a conditional Irf4 or Irf8 allele is deleted in CD11c+ cells, we determined if IRF4 or IRF8 deficiency beginning in CD11c+ cDC precursors (pre-cDCs) changed the homeostasis of mature DCs or pre-DCs in the lung, dermis and spleen. CD11c-cre-Irf4−/− mice selectively lacked a lung-resident CD11chiCD11b+SIRPα+CD24+ DC subset, but not other lung CD11b+ DCs or alveolar macrophages. Numbers of CD11b+CD4+ splenic DCs, but not CD11b+ dermal DCs, were reduced, indicating cDC2s in the lung and dermis develop via different pathways. Irf4 deficiency did not alter numbers of cDC1s. CD11c-cre-Irf8−/− mice lacked lung-resident CD103+ DCs and splenic CD8α+ DCs, yet harbored increased IRF4-dependent DCs. This correlated with a reduced number of Irf8−/− pre-cDCs, which contained elevated IRF4, suggesting that Irf8 deficiency diverts pre-cDC fate. Analyses of Irf4 and Irf8 haploinsufficient mice showed that while one Irf4 allele was sufficient for lung cDC2 development, two functional Irf8 alleles were required for differentiation of lung cDC1s. Thus, IRF8 and IRF4 act in pre-cDCs to direct the terminal differentiation of cDC1 and cDC2 subsets in the lung and spleen. These data suggest that variation in IRF4 or IRF8 levels resulting from genetic polymorphisms or environmental cues will govern tissue DC numbers and therefore regulate the magnitude of DC functional responses.

Myocardial Infarction Primes Autoreactive T Cells through Activation of Dendritic Cells

“…Analysis of Irf4 fl/fl .Cd11cCre mice revealed that cardiac cDC2 (CD172α + CD24 +/− ) were only slightly reduced (Figures 2C and 2E). However, a significant reduction in CD24 + cDC2s was observed, suggesting that IRF4 is important for their terminal differentiation, as described in the lung (Bajaña et al., 2016). Because IRF4 has also been implicated in regulating cDC2 migration (Bajaña et al., 2012), we next studied cDC2 frequency in the heart-draining mediastinal lymph node (mLN) (Figures 2D and 2E).…”

“…As described in other tissues, cDC2s and moDCs expressed CD11b, whereas cDC1s expressed CD103. cDC1s uniformly expressed CD24, whereas cDC2s were separated into CD24 + and CD24 − cDC2s, as described for lung cDC2s (Bajaña et al., 2016). Expression of CADM1, a universal cDC1 marker (Guilliams et al., 2016, Gurka et al., 2015), was restricted to cDC1s.…”

Dendritic Cells Display Subset and Tissue-Specific Maturation Dynamics over Human Life

“…The monocyte and macrophage marker CD64 (Tamoutounour et al, 2012) was highly expressed on CD14 + cells, and expressed at much lower levels on cDC2 and cDC1 (Figure S1A–C), further confirming our subset delineation strategy. In fluorescence images, CD13 + Clec9A + and CD1c + cells displayed a dendritic cell morphology and expressed the canonical cDC1 and cDC2 transcription factors IRF8 and IRF4 (Aliberti et al, 2003; Bajana et al, 2016), respectively (Figure 1F). Our results thus establish human tissue CD13 hi CD141 hi Clec9A + cells as cDC1, and CD1c + Sirp-α + cells as cDC2.…”

Pathogenic TH17 inflammation is sustained in the lungs by conventional dendritic cells and Toll-like receptor 4 signaling

“…The transcription factor BATF3 is required for development of CD103 + cDCs, and these cells are therefore absent in Batf3 −/− mice 39 . A different transcription factor, IRF4, is required for the development of CD11b + cDCs, and mice bearing a floxed allele of Irf4 ( Irf4 fl/fl ) as well as a Cre recombinase gene under control of a Cd11c promoter ( Cd11c-Cre Irf4 fl/fl mice) have markedly reduced numbers of CD11b + cDCs 40 . Surprisingly, after Th17 adoptive transfer and OVA/HDE challenges, Batf3 −/− mice, Cd11c-Cre Irf4 fl/fl mice, and WT mice all had similar levels of airway inflammation, Tomato + Th17 cell numbers and IL-17 cytokine levels (Figure 7A–D).…”