儿童肠道分节丝状菌年龄分布特征及其与肠黏膜免疫的关系

Age distribution characteristics of intestinal segmented filamentous bacteria and their relationship with intestinal mucosal immunity in children

摘要:

目的了解儿童肠道分节丝状菌（SFB）年龄分布特征及其与肠道黏膜免疫的关系。方法收集177例儿童的新鲜粪便及47例儿童肠镜检查时的回盲部肠液，采用RT-PCR法测定SFB，ELISA法测定其sIgA浓度。采用免疫组化方法测定23例儿童回肠末端黏膜IL-17A细胞数量和上皮内淋巴细胞数量及Th细胞分化相关的转录因子T-bet、FOXP3和ROR-γt的表达。结果儿童肠道SFB阳性率为19.2%（34/177）。趋势分析显示SFB阳性率随年龄增加呈降低趋势：0岁~、1岁~、2岁~、3岁~、4岁~、5岁~、6岁~、7~15岁分别为40%、47%、32%、15%、12%、13%、15%、4%（P < 0.001）。SFB阳性患儿（24例）的肠液sIgA浓度明显高于SFB阴性患儿（23例）（P < 0.01）。SFB阳性组（12例）回肠末端黏膜上皮细胞内淋巴细胞数量及转录因子T-bet、FOXP3和ROR-γt的表达与SFB阴性组（11例）的差异无统计学意义，而SFB阳性组回肠末端黏膜IL-17A细胞数量明显低于SFB阴性组（P < 0.05）。结论儿童SFB肠道定植与年龄相关，其中3岁以内婴幼儿SFB肠道定植率较高；SFB阳性者肠道sIgA分泌增加，回肠末端IL-17A细胞数量减少。

Abstract:

Objective To investigate the age distribution characteristics of intestinal segmented filamentous bacteria (SFB) in children and their relationship with intestinal mucosal immunity. Methods The fresh feces of 177 children and the ileocecal fluid of 47 children during colonoscopy were collected. The SFB was determined by real-time PCR. The concentration of secretory immunoglobulin A (sIgA) was determined by enzyme-linked immunosorbent assay. The numbers of interleukin 17A (IL-17A) cells and intraepithelial lymphocytes in the terminal ileum mucosa and the expression of transcription factors associated with the differentiation of T helper (Th) cells, T-box transcription factor (T-bet), forkhead box P3 (FOXP3), and retinoid-related orphan receptor gamma t (ROR-γt), were determined by immunohistochemistry. Results The positive rate of intestinal SFB in these children was 19.2% (34/177). Trend analysis showed that the positive rate of SFB was correlated with age:the rates for children aged 0-, 1-, 2-, 3-, 4-, 5-, 6-, and 7-15 years were 40%, 47%, 32%, 15%, 12%, 13%, 15% and 4% respectively (P < 0.001). The concentration of sIgA in intestinal fluid was significantly higher in SFB-positive children (n=24) than in SFB-negative children (n=23) (P < 0.01). The number of intraepithelial lymphocytes in the terminal ileum mucosa and the expression of T-bet, FOXP3, and ROR-γt were not significantly different between the SFB-positive group (n=12) and the SFB-negative group (n=11), but the number of IL-17A cells in the terminal ileum mucosa was significantly lower in the SFB-positive group than in the SFB-negative group (P < 0.05). Conclusions Intestinal SFB colonization in children is age-related, and the colonization rate is relatively high in children under 3 years old. In SFB-positive children, the secretion of intestinal sIgA is increased, while the number of IL-17A cells in the terminal ileum is reduced.