['Chronic antibiotic-refractory pouchitis (CARP) occurs more frequently in patients with ileal pouch-anal anastomosis (IPAA) with concomitant autoimmune disorders. The aim of this study was to assess the overlap between dysregulated immune features in patients with IPAA and their association with CARP.', 'We identified 150 symptomatic patients with IPAA who met inclusion criteria, including measurement of select autoimmune serology. Demographic and clinical variables were compared between patients with and without CARP.', 'Autoimmune thyroid disease was more frequent among patients with CARP. The frequency of primary sclerosing cholangitis (16.7% versus 5.3%; P = 0.04) and serum positivity for microsomal antibody (25% versus 6.1%, P = 0.003) were significantly greater in patients with CARP compared with non-CARP patients, respectively. Increased tissue infiltration by IgG4-expressing plasma cells was detected in 17 of 31 patients (54.8%) in the CARP group as compared with 10/67 (14.9%) in the non-CARP group (P = 0.0001). Forty-seven percent of patients in the CARP group versus 22.8% in the non-CARP group had at least 2 immune features (P = 0.019). Among patients with IgG4 histology, 87% of patients in the CARP group versus 60% in the non-CARP group had at least 1 immune marker (P = 0.004). On multivariate analysis, microsomal antibody expression (odds ratio, 6.8; 95% confidence interval, 1.3-42.6; P = 0.02) and increased IgG4-expressing plasma cells tissue infiltration (odds ratio, 9.6; 95% confidence interval, 3.2-32.6, P = 0.0001) were risk factors for CARP.'] Are autoimmune features associated with chronic antibiotic-refractory pouchitis?