Coccoid Helicobacter pylori exists in the palatine tonsils of patients with IgA nephropathy

Helicobacter pylori infection is acquired by oral ingestion. H. pylori has been reported to be present in the palatine tonsils. To clarify the route and mode of infection, the prevalence of tonsillar H. pylori was evaluated, and an attempt was made to culture tonsillar H. pylori. In a prospective study, 55 patients with recurrent pharyngotonsillitis or IgA nephropathy underwent a tonsillectomy. The carbon 13-urea breath test and enzyme-linked immunosorbent assay for the detection of H. pylori IgG antibodies in the serum were performed. Tonsillar H. pylori was cultured under conventional culture conditions for gastric H. pylori with or without the following shock methods; heat shock, hydrogen-peroxide-degrading compounds, or parasitizing amoebae. Immunofluorescence and immunoelectron microscopy using antibodies against H. pylori and cytotoxin-associated antigen A were used to identify tonsillar H. pylori. H. pylori in the coccoid form was present in tonsillar crypts. Of 55 patients, 43 (78.2%) had tonsillar H. pylori, and 15 (27.3%) were infected with gastric H. pylori. All patients with gastric H. pylori also had tonsillar H. pylori (p < 0.01). Cytotoxin-associated antigen A was observed in 38 (88.4%) of 43 tonsillar H. pylori. Tonsillar H. pylori could not be cultured in any culture conditions. All patients with IgA nephropathy had tonsillar H. pylori (p < 0.01). The present research might provide some insight into clarifying the route and mode of H. pylori infection. Our findings may indicate that tonsillar H. pylori is one of the antigens causative of IgAN.