Detection of monomeric and polymeric IgA containing immune complexes in serum and kidney from patients with alcoholic liver disease

Abstract

The purpose of this study was to characterize circulating IgA and the IgA deposited in the glomeruli of patients with alcoholic liver disease. In the 6 patients studied there was an increased proportion in monomeric IgA (3.5 fold) and IgA between 9-13S (8.94 fold), 13-17S (4.49 fold) and 17-21S (1.63 fold) fractions on 5-40% sucrose density gradient ultracentrifugation at physiological pH. All fraction between 9.12S decreased at acid pH, however a 3.28 fold increase in fractions where polymeric IgA is expected to appear. IgG eluted at acid pH from autopsy kidney was studied by the same procedures. At pH 7.4 about 55% of that IgA have a molecular weight comprised between 9-12S, decreasing to around 25% at acid pH. The existence of true polymeric IgA in serum and kidney was based on the capacity of high molecular weight IgA to bind human secretory component. The amount of immune complexes with monomeric IgA were higher than those with polymeric IgA in serum as well as in kidney. However, the percentage of heavy IgA (probably polymeric IgA) in kidney were, in each patient, higher than those observed in serum. Our results show the presence of high amounts of monomeric and polymeric IgA, both partially as immune complexes, in serum and kidneys of patients with alcoholic liver disease and IgA glomerulonephritis. Furthermore, our data suggest a role for human liver in the clearance of serum IgA such as has been demonstrated in the some animal species, especially in rats.