Comparative studies on immunoglobulins,complement component (C3), albumin,and immunoglobulin A-containing circulating immune complexes in serum and bile of patients with biliary obstruction

We measured the concentrations of IgA, IgG, IgM, secretory IgA, albumin, complement component (C3), and IgA-containing circulating immune complex (IgA-CIC) in the serum and bile of patients with biliary obstruction. The bile-to-serum (BS) ratio of the concentrations of albumin and IgG increased with the increase in total serum bilirubin. This indicates that the permeability from blood to bile increases with the degree of biliary obstruction, and the blood-bile barrier function breaks down. The BS ratios of IgA and IgM, which are selectively secreted into bile, did not show a significant correlation with total serum bilirubin. The index of the BS ratio to the BS ratio of albumin (BS/BS-Alb index) of IgA and IgM was significantly larger than that of IgG. This indicates that the selective transport of IgA and IgM into bile is present even in patients with obstructive jaundice. Since the BS/BS-Alb index of C3 is larger than that of IgG, and the SGOT correlated directly with the BS ratio of C3, some of the C3 in bile may come from damaged hepatocytes.