Background: Human leukocyte antigen (HLA)-G, a member of the HLA family, is crucial for fetomaternal tolerance. Transmembrane or circulating/soluble HLA-G (sHLA-G) is elevated in autoimmune conditions and the tumor microenvironment. Circulating sHLA-G levels and their association with disease activity have not yet been assessed in pediatric patients with inflammatory bowel disease (IBD). This study aimed to quantify the serum sHLA-G levels of pediatric patients with IBD and assess the association of serum sHLA-G with disease activity. Methods: We enrolled 24 pediatric IBD patients Crohn's disease (CD) and ulcerative colitis (UC), n = 12 each] and 24 healthy controls. Based on the disease activity index, five and seven of the CD patients had mild and moderate/severe disease, respectively, whereas six of the UC patients were in remission and six had mild disease. Serum was collected and sHLA-G levels were determined by enzyme-linked immunosorbent assay (ELISA). Results: Pediatric patients with CD had significantly higher sHLA-G levels compared with patients with UC and healthy controls. Notably, serum sHLA-G levels were significantly higher in patients with moderate/severe CD than in those with mild CD. Conclusions: Serum sHLA-G levels correlate with disease activity in pediatric patients with CD and are higher in CD patients than in UC patients. Thus, sHLA-G is a potential biomarker for disease activity in CD.

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