Abstract
An aberrant mucosal immune response against commensal bacteria in the tonsils is hypothesized to be one of the pathogenic mechanisms underlying immunoglobulin A nephropathy (IgAN). However, the bacteria involved in the pathogenesis of IgAN have not been fully elucidated. In this study, we compared the differences in tonsillar bacterial flora between IgAN (n = 101) and recurrent tonsillitis (RT) (n = 117) based on swab cultures from tonsillar surfaces and the center of the tonsils. The association between Neisseria sp. presence in the tonsils and the clinical course of patients with IgAN who underwent tonsillectomy (n = 81) was investigated. Significant differences in the detection rates of Neisseria sp. on tonsillar surfaces were observed between the IgAN and RT groups (88.0 and 74.4%, respectively). Among the 81 patients, the rates of clinical remission, disappearance of proteinuria, renal function preservation, and renal survival were significantly higher in patients with Neisseria sp. present on the tonsillar surface than in those without. The Cox proportional hazards model indicated the presence of Neisseria sp. on the tonsillar surface as an independent favorable factor for the rates of clinical remission, decreasing renal function, and renal death (hazard ratios: 3.42, 0.03, and 0.06, respectively). However, there were no significant differences in the clinical course, except for renal survival rates, between patients with and without Neisseria sp. at the tonsillar center. This study revealed Neisseria sp. was more frequently found on the tonsillar surface of patients with IgAN than those with RT, and their presence was linked to better clinical outcomes following tonsillectomy.