Study of the regulatory function for immune and allergic responses by the intestinal microbacteria and probiotic bacteria

肠道中肠道细菌的结合被认为有助于肠道免疫系统的发育和维持稳态。功能性肠道微生物或益生菌预计将调节宿主的免疫反应或调节过敏反应。然而，肠道细菌对肠道免疫系统的免疫功能尚未阐明。通过建立卵清蛋白（OVA）特异性T细胞受体转基因（OVA-Tg）小鼠的非益生菌模型，研究肠道细菌对肠道免疫应答的直接影响。使用这些小鼠，我们研究了假小链双歧杆菌7041（Bp）的联合对派伊尔集合淋巴结（PP）免疫应答的影响，派伊尔集合淋巴结是肠道免疫系统的诱导部位。无菌OVA-Tg小鼠与（Bif）或无（Cont）Bp相关，然后与分节丝状细菌和梭菌相关。这些小鼠被喂食标准饮食或蛋清饮食。分析PP细胞对OVA的细胞因子应答作为所接受饮食的函数。与Cont小鼠相比，喂食标准饮食的Bif小鼠的PP细胞对OVA的应答显示出较低水平的IFN-γ和IL-6产生。此外，当小鼠被喂食蛋清饮食时，Bif小鼠的PP细胞显示出比Cont小鼠更低的IFN-γ和IL-6产生水平。与无菌小鼠相比，Bif小鼠的这些细胞因子产生模式与常规小鼠相似。结果表明，Bp的关联下调PP细胞对饮食抗原的过度细胞因子产生，并可能有助于诱导正常肠道免疫反应的发展。

The association of intestinal bacteria in the gut is considered to contribute to the development and maintaining homeostasis of intestinal immune systems. Functional intestinal microbacteria or probiotics are expected to modulate the immune responses or regulate allergic reactions in the host. However, the immune function of intestinal bacteria on intestinal immune systems has not been clarified. We examined the direct effects of intestinal bacteria on intestinal immune responses to dietary antigen by establishing a gnotobiotic model of ovalbumin (OVA) specific T cell receptor transgenic (OVA-Tg) mice. Using these mice, we examined the effects of the association of Bifidobacterium pseudocatenulatum 7041 (Bp) on immune responses by Peyer's patches (PP), which are inductive sites of the intestinal immune system. Germ-free OVA-Tg mice were associated with (Bif) or without (Cont) Bp and then associated with segmented filamentous bacteria and clostridia. These mice were fed a standard diet or an egg-white diet. Cytokine responses to OVA by PP cells were analyzed as a function of the diet received. PP cells of Bif mice fed a standard diet showed lower levels of IFN-γ and IL-6 production in response to OVA than those of Cont mice. In addition, when mice were fed an egg-white diet, PP cells of Bif mice showed lower levels of IFN-γ and IL-6 production than those of Cont mice. These patterns of cytokine production of Bif mice were similar to those of conventional mice compared with germ-free mice. The results suggest that the association of Bp downregulated excessive cytokine production by PP cells in response to dietary antigen and might contribute to induce the development of normal intestinal immune responses.