Methods

Patients (Table 1). Three groups were studied: Group 1: Primary IgA nephropathy (78 patients). These patients presented with macroscopic hematuna, asymptomatic proteinuria, hypertension, or renal insufficiency. All had at least one renal biopsy sample examined by light, electron, and immunofluorescent microscopy, as previously described [5]. The patients in this group all had diffuse mesan-gial deposits of IgA, which were usually accompanied by C3 (82%) and less commonly by 1gM (43%), IgG (22%), and Clq (14%). In all instances, IgA was the principal immunoglobulin detected. Light microscopy showed mesangial enlargement with or without focal and segmental features, and electron microscopy confirmed the presence of mesangial deposits and increased mesangial cyto-plasm and matrix. Details of the morphologic findings in 50 of these patients have been reported pre-viously [5]. Patients with clinical evidence of liver disease or of systemic disease (skin rash, arthralgia, and so on) were excluded as were patients with a positive test for antinuclear antibodies. Group 2: IgA glomerulonephritis associated with alcoholic cirrhosis, portal systemic shunts, or both (10 patients). The patients in this group had macroscopic hematuria, proteinunia, hypertension, or re-nal insufficiency in association with alcoholic cir-rhosis and/or portal systemic shunts. Nine had alcoholic cirrhosis, two with portacaval shunts, and one patient had a lienorenal shunt for primary portal vein thrombosis. Renal biopsy findings were gener-ally similar to those in primary IgA nephropathy. All patients has mesangial deposits of IgA, and in addition many had C3 (90%), 1gM (63%), IgG (50%), and Clq (50%). Electron microscopy demonstrated mesangial and subendothelial dense deposits and, in some patients, the membrane and matrix lucencies described in glomerulonephritis associat-ed with alcoholic cirrhosis [13]. None of the patients was positive for hepatitis B virus antigen or antibody.

Group 3: Henoch Schonlein purpura (HSP)(6 patients). These patients presented with the characteristic features of skin rash, arthralgia, and glomerulonephritis. In addition, one patient had abdominal pain and gastrointestinal bleeding. All patients had mesangial deposits of IgA and C3. Sera. Blood was collected, if possible, at the time of the initial renal biopsy and then at 3 to 6 monthly intervals. Samples (N= 264) were collected from the 78 patients with primary IgA nephropathy, 57 from the 10 patients in group 2 and 26 from the 6 patients with HSP. Blood samples were also collected from 80 control subjects (hospital staff and healthy blood donors). The serum was separated by centrifugation at room temperature and stored in aliquots at—70 C. Blood samples for the detection of cryoglobulins (performed in 20 patients) were collected in a warmed syringe, allowed to clot at 37 C, and the serum held at 4 C for 3 days. Serum immuno globulin and complement concen-trations. Serum IgA, IgG, 1gM, C3, and Clq con-centrations were measured by radial immuno-diffusion.