IL-4-BATF signaling directly modulates IL-9 producing mucosal mast cell (MMC9) function in experimental food allergy

Abstract Background We have previously identified IL-9 producing mucosal mast cell (MMC9) as the primary source of IL-9 to drive intestinal mastocytosis and experimental IgE-mediated food allergy. However, the molecular mechanisms that regulate the expansion of MMC9s remain unknown. Objective We hypothesized that IL-4 regulates MMC9 development and MMC9-dependent experimental IgE-mediated food allergy. Methods We utilized an epicutaneous sensitization-model and performed bone marrow (BM) reconstitution experiments, to test the requirement of IL-4Rα signaling on MMC9's in experimental IgE-mediated food allergy. Flow cytometric, bulk and single cell RNA-seq analysis on small intestine (SI)-MMC9s was performed to illuminate MMC9 transcriptional signature and the effect of IL-4Rα signaling on MMC9 function. BM-derived MMC9 culture system was used to define IL-4-BATF signaling in MMC9 development. Results Epicutaneous sensitization and BM reconstitution based models of IgE-mediated food allergy revealed an IL-4 signaling-dependent cell-intrinsic effect on SI- MMC9 cell accumulation and food allergy severity. RNA-seq analysis of SI-MMC9 cells identified 410 gene transcripts reciprocally regulated by IL-4 signaling, including Il9 and Basic leucine zipper ATF-like transcription factor (Batf). In silico analyses identified a 3491-gene MMC9 transcriptional signature and identified two transcriptionally distinct SI-MMC9 populations enriched for metabolic or inflammatory programs. Employing an in vitro MMC9-culture model system we show that generation of MMC9-like cells was induced by IL-4 and this was in part dependent on BATF. Conclusion IL-4Rα signaling directly modulates MMC9 function and exacerbation of experimental IgE-mediated food allergic reactions. IL-4Rα regulation of MMC9s is in part BATF-dependent and via modulation of metabolic transcriptional programs.