Supplementary Material for: Potential for CCR9+ IL-17+ Regulatory T Cell as a Predictor of Early Necrotizing Enterocolitis

Background: Circulating CCR9+ IL-17+ regulatory T (Treg) cells and intestinal barrier biomarkers, such as trefoil factor 3 (TFF3), intestinal-fatty acid binding protein (I-FABP), and Zonulin, are associated with gastrointestinal inflammatory diseases. So far, it is still difficult for clinicians to predict early necrotizing enterocolitis (NEC). Study Design: This study included 13 patients with stage I NEC-like presentation (early NEC), 24 patients with one stage of II or III NEC (confirmed NEC), and 80 non-NEC and nonsepsis preterm infants (control group). Another 16 patients experienced at least two stages. We used flow cytometry to measure the frequency of CCR9+ IL-17+ Treg cells and enzyme-linked immunosorbent assay to measure TFF3, I-FABP, and Zonulin levels in the peripheral blood. Results: The demographic and clinical characteristics of patients were comparable. Compared with controls, CCR9+ IL-17+ Treg cells were markedly increased in early NEC and slightly increased in confirmed NEC; in contrast, plasma TFF3, I-FABP, and Zonulin concentrations were notably elevated in confirmed NEC and slightly elevated or not elevated in early NEC. Moreover, for patients who experienced at least two stages, dynamic monitoring of the above indicators also verified this. Conclusions: This study suggested that an elevated frequency of circulating CCR9+ IL-17+ Treg cells could be a predictor of intestinal inflammation in patients with early NEC.