Comparative analysis of the tonsillar microbiota in IgA nephropathy and other glomerular diseases

Immunoglobulin A nephropathy (IgAN) involves repeated events of gross haematuria, with concurrent upper airway infections. The mucosal immune system, especially the tonsil, is considered the initial site of inflammation in IgAN; however, the role of the tonsillar microbiota has not been established. In this study, we compared the tonsillar microbiota of patients with IgAN (n = 21) and glomerular diseases (n = 36) as well as healthy controls (n = 23) from three medical centres in Korea. The microbiota was analysed from tonsil swabs using the Illumina MiSeq system based on 16S rRNA gene. Tonsillar bacterial diversity was higher in IgAN than in other diseases, although diversity did not differ from that of healthy controls. Principal coordinates analysis revealed differences between the tonsillar microbiota of IgAN and both healthy and disease controls. The proportions of Rahnella, Ruminococcus_g2, and Clostridium_g21 were significantly higher in patients with IgAN than in healthy controls (corrected p < 0.05). The relative abundances of several taxa were correlated with the estimated glomerular filtration rate, blood urea nitrogen, haemoglobin, and serum albumin levels. Based on our findings, tonsillar microbiota could contribute to the immune changes, pathogenesis, and clinical features of IgAN.