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[Age distribution characteristics of intestinal segmented filamentous bacteria and their relationship with intestinal
Wei-Rong Liu1, Xiao-Li Shu, Wei-Zhong Gu
1Department of Gastroenterology, Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China. mizu@zju.edu.cn.
Insights
Intestinal segmented filamentous bacteria (SFB) colonization is common in young children, peaking under age three. SFB presence correlates with increased intestinal secretory IgA but reduced IL-17A cells in the terminal ileum.
Area of Science:
- Microbiology
- Immunology
- Pediatrics
Background:
- Segmented filamentous bacteria (SFB) are commensal microorganisms residing in the rodent gut, known to influence host immunity.
- The role and prevalence of SFB in human intestinal ecosystems, particularly in children, remain less understood.
- Understanding SFB's age-related distribution and its impact on developing mucosal immunity is crucial for pediatric health research.
Purpose of the Study:
- To determine the age-specific prevalence of intestinal SFB in a pediatric cohort.
- To investigate the association between SFB colonization and key markers of intestinal mucosal immunity, including secretory IgA (sIgA) and T helper cell-related cytokines.
- To explore the relationship between SFB and the expression of transcription factors (T-bet, FOXP3, ROR-γt) involved in T cell differentiation.
Main Methods:
- Collected fecal samples from 177 children and ileocecal fluid from 47 children for SFB detection via real-time PCR.
- Quantified secretory immunoglobulin A (sIgA) concentration using enzyme-linked immunosorbent assay.
- Assessed the density of interleukin 17A (IL-17A) cells and intraepithelial lymphocytes, along with T-bet, FOXP3, and ROR-γt expression in terminal ileum mucosa via immunohistochemistry.
Main Results:
- The overall prevalence of intestinal SFB was 19.2%, with significantly higher rates in children under three years old (40-47%).
- SFB-positive children exhibited significantly higher levels of intestinal sIgA compared to SFB-negative children.
- While intraepithelial lymphocytes and key transcription factor expressions were similar, SFB-positive children showed a significant reduction in IL-17A cells in the terminal ileum.
Conclusions:
- Intestinal SFB colonization in children is strongly age-dependent, with a high colonization rate observed in those under three years of age.
- SFB colonization is associated with enhanced intestinal sIgA secretion, suggesting an impact on humoral immunity.
- A notable finding is the reduced presence of IL-17A-producing cells in the terminal ileum of SFB-colonized children, indicating a potential modulation of Th17-mediated immunity.
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.
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