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.
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。