The Role of Urinary Secretory Immunoglobulin A in the Pathophysiology of Interstitial Cystitis

This study aimed to determine whether urinary secretory immunoglobulin A (sIgA) levels differ between patients with bladder pain syndrome/interstitial cystitis (BPS/IC) and healthy controls, and to assess whether urinary sIgA is linked to mucosal immune mechanisms that may contribute to BPS/IC pathophysiology.

A single-center, cross-sectional study was conducted between April and June 2020 at the Department of Urology, Ege University Faculty of Medicine. Forty female patients with BPS/IC and 40 healthy controls were enrolled. Symptom severity in the BPS/IC group was evaluated using the O'Leary-Sant Interstitial Cystitis Symptom and Problem Index. Patients with active urogenital infections, a history of bladder cancer, or prior pelvic radiotherapy were excluded. Urine samples were collected in sterile containers, centrifuged, and stored at -80°C before sIgA measurement using a commercial enzyme-linked immunosorbent assay kit. Correlations between continuous variables were examined with Spearman rank correlation coefficients.

Urinary sIgA levels were not significantly different between the BPS/IC group (mean±standard deviation: 0.96±1.5 μg/mL) and healthy controls (0.53±0.7 μg/mL) (P=0.173). Subgroup analyses within the BPS/IC cohort showed that smokers had significantly lower urinary sIgA levels (median [range], 0.001 [0.000-0.082] μg/mL) compared with nonsmokers (median [range], 0.720 [0.000-6.850] μg/mL) (P=0.004). Conversely, patients with cardiac comorbidities had significantly higher urinary sIgA levels (median [range], 0.820 [0.100-6.850] μg/mL) than those without cardiac disease (median [range], 0.213 [0.000-2.300] μg/mL) (P=0.015).

Although no significant differences in urinary sIgA levels were observed between BPS/IC patients and healthy controls, subgroup analyses identified associations with smoking and cardiac comorbidities. These findings suggest that sIgA may be relevant to BPS/IC pathophysiology and highlight the potential of mucosal immune biomarkers. Larger studies are warranted to further clarify the role of sIgA in BPS/IC.