<i>Neisseria</i> species on the tonsillar surface predicts favorable clinical outcomes in patients with Immunoglobulin A nephropathy who underwent tonsillectomy

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 (<i>n</i> = 101) and recurrent tonsillitis (RT) (<i>n</i> = 117) based on swab cultures from tonsillar surfaces and the center of the tonsils. The association between <i>Neisseria</i> sp. presence in the tonsils and the clinical course of patients with IgAN who underwent tonsillectomy (<i>n</i> = 81) was investigated. Significant differences in the detection rates of <i>Neisseria</i> 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 <i>Neisseria</i> sp. present on the tonsillar surface than in those without. The Cox proportional hazards model indicated the presence of <i>Neisseria</i> 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 <i>Neisseria</i> sp. at the tonsillar center. This study revealed <i>Neisseria</i> 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.