Mapping the epigenetic landscape of murine eosinophils

Abstract

setts General Hospital. RATIONALE: Dendritic cells (DCs) are innate immune sentinels. Upon encounter with pathogens, they mature and migrate to draining lymph nodes (dLNs), where they can initiate adaptive immune responses. The process by which Th2 immunogens lead to this response is unclear. We recently showed that Th2-skewing CD301b + DCs upregulate CCR8 after allergen stimulation in na€ ıve mice, which was required for DCs entry into the dLN parenchyma and subsequent Th2 responses. This was dependent on production of the CCR8 ligand, CCL8, by interfollicular region macrophages (IFR macs). Thus, IFR macrophages likely have the ability to remotely sense Th2 immunogens. In this study, we capitalized on the allergen-sensing ability of IFR macs to identify mechanisms of Th2 immunogen sensing. METHODS: IFR macs were enriched using magnetic-activated cell sorting of SIGN-R1 + cells in digested lymph nodes. Bone marrow-derived macrophages (BMDMs) were generated from C57Bl/6 mice. RNASeq analysis and QPCR was performed to assess gene expression. RESULTS: IFR macs and BMDMs treated in vitro with papain and other cysteine protease immunogens upregulated Ccl8, while treatment with LPS did not. Papain-induced Ccl8 expression was dependent on serum, although supplementation of media with gamma globulin or albumin alone was not permissive for papain-induced Ccl8 epxression. RNA-seq analysis of BMDMs treated with papain demonstrated multiple differentially-regulated pathways. CONCLUSIONS: Macrophages produced Ccl8 directly in response to cysteine protease allergens in a serum-dependent fashion. This suggests that papain is sensed by a serum component, which is recognized by macrophages. Transcriptomic analysis gives clues to the mechanisms by which this occurs.