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

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.