IgA deposition in alcoholic liver disease. An immunoelectron microscopic study

The ultrastructural localization of IgA, IgA1, and IgA2 deposited on liver tissues from 13 patients with alcoholic liver disease and 9 patients with nonalcoholic liver diseases was investigated by the immunoperoxidase method. A continuous pattern of IgA deposition along the perisinusoidal area was observed not only in the alcoholic patients but also in the nonalcoholic patients. Ultrastructurally, IgA deposits were seen on the plasma membranes of Kupffer cells, endothelial cells, and hepatocytes and in the endocytotic vesicles and phagosomes of Kupffer cells and endothelial cells. In the alcoholic group, deposits of IgA on collagen fibers were observed at sites where pericellular fibrosis developed but, on the other hand, IgA deposits were diminished or absent on the plasma membranes of hepatocytes. IgA1 showed the same deposit pattern as IgA. IgA2 was observed on and in Kupffer cells and endothelial cells but was not detected on the plasma membranes of hepatocytes. From these studies, the authors conclude that IgA deposition in the liver is not specific for alcoholic liver disease but may reflect the reduced metabolism of damaged liver. An additional finding was that, of the IgA subclasses, only IgA1 combined with the plasma membranes of hepatocytes.