Tonsillar TLR9 expression and efficacy of tonsillectomy with steroid pulse therapy in IgA nephropathy patients

Background. Patients with IgA nephropathy (IgAN) often show aggravation of renal injury with macroscopic hematuria after mucosal infections, especially tonsillitis. We previously demonstrated the important role of mucosal Toll-like receptor 9 (TLR9) activation in the pathogenesis of murine IgAN. Moreover, a single nucleotide polymorphism (SNP) in TLR9 was significantly associated with pathological severity in human IgAN. In this study, we investigated correlations between tonsillar TLR9 messenger RNA expression, TLR9 SNP genotypes and clinical outcomes following tonsillectomy with steroid pulse therapy (SPT) in IgAN patients. Methods. Tonsillar TLR9 expression was examined in IgAN (n ¼ 49) and control (n ¼ 15) patients who had undergone tonsillectomy. The correlations between tonsillar TLR9 expression level, TLR9 SNP genotypes and clinical outcomes after tonsillectomy with SPT were examined. Results. High expression of tonsillar TLR9 was observed in ~23% of IgAN patients. These patients showed stronger and earlier remission of hematuria and proteinuria than those with low TLR9 expression. Patients with the TT genotype of TLR9 SNP (rs352140) had more severe renal damage than those with other genotypes. Patients whose serum IgA level decreased more than average after tonsillectomy (large DIgA) showed higher cumulative remission rates of proteinuria than patients with a smaller decrease in these levels (small DIgA). CT/CC genotypes were more dominant and tonsillar TLR9 expressions significantly higher in large DIgA patients than in small DIgA patients. Conclusion. In IgAN patients, expression levels of tonsillar TLR9 and TLR9 SNP were well correlated with the efficacy of tonsillectomy with SPT.