Phagocytic activity of polymorphonuclear leucocytes in patients with IgA nephropathy

The phagocytic activity of polymorphonuclear leucocytes (PMN) in 57 patients with IgA nephropathy was investigated using Immunobeads. Depressed activity was detected in 41 patients (72%). A significant correlation existed between the ingestive function of neutrophils and glomerular histological abnormalities, such as the degree of mesangial proliferation. In addition, 25 patients with IgA nephropathy were studied to detect the presence of immunological inclusions in the PMN by a direct immunofluorescent technique (anti-IgG, IgA, IgM and C3). Intracytoplasmic inclusions containing IgA were frequently detected in the PMN, and a negative correlation was found between the percentage of IgA-positive PMN and the phagocytic activity of neutrophils in patients with IgA nephropathy. These results suggest that the activity of neutrophils represents one of the important factors in the pathogenesis of IgA nephropathy and that mesangial IgA deposition is partly caused by decreased clearance activity of PMN.