Therefore, we speculated that PDIA3 may promote endogenous antigen presentation to increase the sensitivity and reactivity of DCs to the antigens, resulting in excessive immunity of T cells to overproduce IL-4 and IL-9, leading to the generation of highly sensitive MC, or even granulated MC, activated protease activating receptor-2 (PAR-2), and consequently visceral hypersensitivity in IBS (Zhuang et al., 2015). Here, IL9 is linked to irritable bowel syndrome.