Abstract: Objective To detect the sera anti-enteric neuronal antibodies (AENA) in irritable bowel syndrome with diarrhea (IBS-D) patients and analyzed its correlation with IBS-D symptoms to explore the potential roles of AENA in the pathogenesis of IBS. Methods IBS-D patients met the Rome III diagnostic criteria were enrolled in this study. The sera of healthy subjects were used as controls. Indirect immunofluorescence (IIF) was used to detect the sera AENA with the substrate of ileal submucosal plexus of guinea pig. The immune reactivity (IR) stains were read in blinded method. The bowel symptoms of patients with positive AENA were compared to that with negative and weekly positive antibodies. Results 1) A total of 127 IBS-D patients were enrolled in this study. The positive rate of sera AENA was 85.8% in IBS-D patients, and 7.0% in healthy controls. Among 109 IBS-D patients with positive IIF reactivity, 23.6% present with strong positive, 43.3% with positive and 18.9% with weakly positive stain. The IR patterns include cytoplasm staining, nucleus staining, cytoplasms and nuclei staining , nuclear membrane staining, cytoplasm and nuclear membrane staining. Six positive sera of healthy control showed cytoplasm staining to substrate neurons. 2) More patients of IBS-D with positive IR have higher intestinal symptoms scores (>10 scores, 58.8% vs 38.1%), frequent abdominal pain in non-defecation period (91.7% vs 60.0%), and severe abdominal pain/discomfort before defecation (24.7% vs 9.5%) comparing to those with negative and weekly positive IR of AENA; IBS-D patients with positive IR of AENA are more commonly associated with urgency comparing to those with negative IR in IIF (57.1% vs 87.3). Conclusions The results indicate AENA might play a role in the pathogenesis of IBS, and is expected to become the biomarker of IBS.

Key words: irritable bowel syndrome, anti-enteric neuronal antibodies, enteric nervous system, biomarker