Study of the mucosal immunomoduLation by intestinal commensal bacteria

肠道寄生菌在调节肠道免疫应答如抗过敏反应、抗感染等方面发挥重要作用。研究表明，肠道细菌极大地影响肠道相关淋巴组织的发育和肠道中的粘膜免疫应答，如伊加的产生。考虑到大量的肠道微生物群，特别是在大肠中，认为大肠中的免疫细胞受到微细菌的调节。虽然先前已经研究了小肠中免疫细胞的伊加产生，但是对大肠中伊加的产生知之甚少。在这项研究中，我们表明，IgA的淋巴细胞的生产是由大肠中存在的微生物诱导的。大肠固有层淋巴细胞（L-LP）分离自无菌（GF）和常规（CV）小鼠。L-LP淋巴细胞的流式细胞术分析用于评估IgM+B220+细胞的频率。 关于我们 ls、伊加+B220+细胞和伊加+Syndecan-1 +B220-细胞。此外，为了确定肠道细菌刺激是否影响IgM+细胞向IgA-浆细胞的分化，将从GF小鼠的L-LP淋巴细胞分离的IgM+细胞与从CV小鼠的肠道细菌分离的产酸拟杆菌共培养。GF的L-LP中伊加+Syndecan-1+B220-细胞和伊加+B220+细胞的频率均低于CV小鼠，GF和CV小鼠L-LP中IgM+13220+细胞的频率无差异。由B刺激的IgM+细胞的伊加产生。结果表明，B的直接刺激作用可使细菌对大肠杆菌的刺激作用增强。产酸杆菌诱导IgM+细胞分化为来自大肠的IgA产生性浆细胞。这也表明，大肠中伊加的产生可能是由肠道细菌诱导的，因此肠道微生物促进了大肠中IgM向伊加的类别转换。少

Intestinal commensal bacteria play important roles in the regulation of intestinal immune responses such as anti-allergic reaction and anti-infection. It has been shown that intestinal commensal bacteria greatly affect the development of gut-associated lymphoid tissues and mucosal immune responses, such as IgA production, in the gut. Given the large numbers of intestinal microbiota, particularly in the large intestine, it is believed that immunocytes in the large intestine are modulated by microbacteria. While IgA production by immunocytes in the small intestine has been previously studied, IgA production in the large intestine is, however, poorly understood. In this study, we show that IgA production by lymphocytes is induced by microbacteria present in the large intestine.Lamina propria lymphocytes from the large intestine (L-LP) were isolated from germ-free (GF) and conventional (CV) mice. Flow cytometric analysis of L-LP lymphocytes was used to assess the frequency of IgM+B220+ cel … More ls, IgA+B220+ cells, and IgA+Syndecan-l+B220- cells. In addition, to determine whether stimulation by commensal bacteria influences differentiation of IgM+ cells into IgA-plasma cells, IgM+ cells separated from L-LP lymphocytes of GF mice were co-cultured with Bacteroides acidofaciens isolated from intestinal commensal bacteria of CV mice.The frequency of IgA+Syndecan-1+B220- cells and IgA+B220+ cells in L-LP of GF were all lower than that of CV mice, but there was no difference in the frequency of IgM+13220+ cells in L-LP between GF and CV mice. IgA production by IgM+ cells stimulated by B. acidofaciens was higher than in those without bacterial stimulation.These results indicate that direct stimulation by B. acidofaciens induces differentiation of IgM+ cells into IgA-producing plasma cells from the large intestine. These also suggest that IgA production in the large intestine might be induced by intestinal commensal bacteria, thus intestinal microbacteria promote the class switching from IgM to IgA in the large intestine. Less