Platelet-derived growth factor mesangial deposits in mesangial IgA glomerulonephritis.

Platelets may play a role in the pathogenesis of IgA glomerulonephritis (IgAGN). Ultrastructural labelling of platelet antigens might identify activated platelets, and localisation of platelet antigens may assist in understanding the role of platelets in glomerular disease. We examined renal biopsies from eight patients with mesangial IgAGN using protein A-gold immunoelectron microscopy. Serial sections were stained with antisera against platelet-derived growth factor (PDGF), platelet factor 4, beta-thrombolglobulin, platelet glycoprotein IIb-IIIa complex, and fibrinogen, as well as antisera against IgA, IgG, IgM and C3c. Platelets, including activated and degranulated platelets, were detected in capillaries in five of eight biopsies. PDGF was detected in mesangial deposits in five of eight cases. In one case immunolabelling was as intense as IgA labelling. Fibrinogen labelling was present in six of eight. Less intense labelling or negative results were obtained with the other antisera. There was no correlation between intensity of immunolabelling and any clinical or morphological features reflecting severity of glomerular lesions. The role of platelets in the pathogenesis of IgAGN remains unclear. The documentation of frequent deposit of PDGF should stimulate further interest in PDGF participation in this condition.