Helicobacter pylori and T Helper Cells: Mechanisms of Immune Escape and Tolerance

Figure 2

The impaired Th17/Treg balance. The induction of Treg cell differentiation is mediated by the overexpression of B7-H1 due to H. pylori cag PAI [41]. On the other hand, the CagA-induced lowered B7-H2 signaling inhibits Th17 cells development from naïve T CD4+ cells [42]. The higher expression of IDO downregulates IL-17 production [36]. DCs promote Tregs differentiation through higher production of IL-18 [44] as well as by a transforming growth factor- (TGF-) β/IL-10-dependent mechanism, which in turn blocks the Th17 cell proliferation [43]. The efficiency of Treg cells themselves is impaired by the production of IL-1β enhanced by the bacterium [47].