Intestinal immune tolerance is maintained through the interplay between commensal microbiota, immune cells and epithelium. Constitutive intestinal epithelial-secreted interleukin (IL)-7 facilitates the proliferation and thus maintenance of gamma-delta T lymphocytes, which preserves intestinal mucosal immune surveillance. Since IL-7 is essential for maintaining intestinal health, we hypothesised that microbiota-derived components influenced by dietary kiwifruit support the intestinal IL-7 expression. In vitro gastro-ileal digestion and colonic fermentation of gold and green kiwifruit generated soluble bacteria-free fermenta, notably bacterial DNA that modulated basal and interferon gamma-stimulated IL-7 secretion in HT-29 cells. Epithelial IL-7 secretion correlated positively with total bacterial DNA, and the DNA originated from bifidobacteria, which are known to contain immunostimulatory CpG motifs. These findings demonstrate the involvement of microbiota DNA in promoting IL-7 secretion in the intestinal epithelium and contribute to unravelling a mechanism by which kiwifruit serve to maintain intestinal immune homeostasis.

肠道免疫耐受是通过共生菌群，免疫细胞和上皮细胞之间的相互作用来维持的。本构肠上皮分泌白介素（IL）-7促进了γ-δT淋巴细胞的增殖并因此得以维持，从而保留了肠粘膜免疫监视。由于IL-7对于维持肠道健康至关重要，因此我们假设受饮食猕猴桃影响的微生物群衍生成分支持肠道IL-7表达。体外黄金和绿色奇异果的肠胃回肠消化和结肠发酵产生可溶的无细菌发酵罐，尤其是细菌DNA，可调节HT-29细胞中基础和干扰素γ刺激的IL-7分泌。上皮IL-7分泌与细菌总DNA和源自双歧杆菌的DNA呈正相关，而双歧杆菌的DNA包含免疫刺激性CpG基序。这些发现表明微生物群DNA参与促进肠上皮中IL-7的分泌，并有助于揭示猕猴桃用来维持肠免疫稳态的机制。