Intrahepatic synthese of immunoglobulin G in chronic liver disease.

A method has been developed to measure the in vitro production of immunoglobulin (Ig) by liver biopsy specimens. Five to 30 mg of liver tissue was cultured for 24 h in Dulbecco's modified Eagle's medium/10% foetal calf serum (FCS) containing radiolabelled leucine (L-[4,5-3H] leucine). The culture medium was collected, centrifuged and the supernatant dialysed to remove labelled leucine. The residual radioactivity was a measure of newly synthesized 3H-labelled proteins released into the medium. The quantity of IgG was determined by immunoprecipitation with monospecific antisera to IgG heavy chains. The presence of IgG in the supernatant was confirmed by chromatography on protein-A Sepharose column. In 6 biopsies without evidence of active inflammation (4 normal and 2 fatty liver by histological criteria) less than 1% of the protein synthesized was IgG. In contrast in the presence of active inflammation in 4 cases of alcoholic hepatitis the IgG percentage ranged from 2 to 6%. Maximal levels of IgG production were detected in 3 cases of chronic active hepatitis (CAH) and ranged from 5 to 30%. The increased Ig synthesis by the liver in alcoholic hepatitis and CAH is presumed to be an index of the intrahepatic host response and may have important implications for mechanisms of liver damage in these diseases.