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. 2021 Oct 11;12:738762. doi: 10.3389/fimmu.2021.738762

Figure 2.

Figure 2

Potential mechanisms of the adaptive immune response towards gut microbiota in homeostasis and chronic inflammation. Under homeostasis, microbiota is restricted to the lumen of the gut by both an epithelial cell layer and a mucus layer, produced by goblet cells and full of antibacterial peptides. Dendritic cells (DCs), M cells and macrophages acquired antigens from the lumen. Antigen presenting cells (APCs) carrying those antigens migrate to Peyer´s patches (PP) where they present the antigens to naïve T cells to prime them. Regulatory CD8+ T cells are able to immunosuppress Tc1 by interleukin (e.g. IL10) release and cell-cell contact, leading Tc1 cells towards anergy, a non-responsive stage, or even re-directed towards a T reg phenotype. Some double positive Foxp3+ IL17+ cells might be in an intermediate stage towards Tc17, relevant cells for mucosal maintenance. Trm cells contribute to the homeostasis of the tissue by releasing IL10. DC, dendritic cell; IL, interleukin; PP, Peyer´s patch; Tc1 or CTL, cytotoxic T lymphocyte; Tc17, IL17-producing CD8+ T cells; T reg, CD8+ T regulatory cell.