Possible mechanisms of elevation of serum secretory immunoglobulin A in liver diseases.

In order to investigate possible mechanisms of elevation of serum secretory immunoglobulin A (sIgA) in liver diseases, human liver specimens were applied to immunohistochemical study of immunoglobulin A, secretory component, and J chain, which are components of sIgA. In the cases of chronic hepatitis with high serum sIgA levels, these antigens were present in dilated bile canaliculi of hepatocytes and they were continuously stained on the lateral plasma membrane of hepatocytes from the bile canaliculus to the space of Disse over the junctional complexes. Furthermore, in liver cirrhosis and extrahepatic cholestasis, they were also detected in intraportal bile ductules and intercellular spaces of degenerated cholangiocytes. These results suggest that at least two pathways might allow elevation of serum sIgA: through the communication of the bile canaliculus with the space of Disse over junctional complexes and through the bile ductule into the portal blood vessel.