We designed a study to investigate the morphological expression of immune responses in the palatine tonsils from patients with IgA nephropathy. To distinguish between the histological characteristics of the tonsils in habitual tonsillitis (47 patients) and IgA nephropathy (11 patients), we studied the T nodules, B-lymphoid follicles, germinal centers, areas of mixed T and B lymphocytes, lacunar epithelium and connective tissues; then we compared patients with habitual tonsillitis and IgA nephropathy. The T nodules in patients with IgA nephropathy were enlarged, and this change was not accompanied by atrophy of B-lymphoid follicles. Morphologically, primary T nodules were predominant. In reactive lymph nodes, T nodules generally play an important role in the extra-follicular maturation of stimulated B lymphocytes into Ig-secreting plasma cells. Therefore the enlarged primary T nodules remind us that this maturation may occur more frequently in the tonsils of patients with IgA nephropathy than in those with habitual tonsillitis. This suggests that some immunoregulatory dysfunction exists in the secretory immune system of mucosa-associated lymphoid tissues in patients with IgA nephropathy.