Different Doses of Allergen Exposure on Dendritic Cells Determine Their Genetic/Epigenetic Regulation and T Cell Differentiation

Background: It has been reported that when DCs are exposed to high-dose antigens, they can induce Th0 cells into regulatory cells (Treg) and Th1 cells. When DCs are subjected to low-dose allergen, they can drive to Th2 cells. However, the mechanisms of such dose-effect relationship are poorly understood so far. Methods: Bone marrow immature DCs (imDCs) were generated from mice and stimulated with OVA of different concentrations (0, 10, 100, 1000, 10000 μg/ml, respectively). The mDCs were then seeded and cocultured with naïve T cells for 3 days, and then the markers of different T cell subgroups were flow cytometrically tested. RNA-seq detection and DNA methylation of DCs were performed. Results: When DCs were stimulated with low-dose (10ug/ml), 77 genes were up-regulated and 87 genes down-regulated. Most activated genes were related to ribosome synthesis and ion channel inhibition but not to the immune responses and Th2 activation. At the medium-dose (100μg/ml), 339 genes were up-regulated and 168 genes down-regulated. Most activated genes involved cytokine synthesis and regulation of immune responses. At high-dose (10000μg/ml), 2794 genes were up-regulated and 1156 genes down-regulated. Tumor necrosis factor signaling pathway, MAPK signaling pathway, antigen processing and presentation signaling pathway were mostly up-regulated. The related co-stimulators, co-inhibitory molecules, inhibitory cytokines, negative regulating enzymes were highly expressed. The monocarbate, coenzyme, fatty acid, glucolipid, starch, sucrose and other metabolism-related signaling pathways were down-regulated. Conclusion: The profiles of DNA methylation and RNA synthesis of DCs varied with different doses of OVA, which serves to induce T cells to differentiate in various directions.