M4 and M9 autoantigens in primary biliary cirrhosis--a negative study

We have investigated the potentially important finding that anti-M9 and anti-M4 antibodies in the sera of patients with primary biliary cirrhosis (PBC) recognise epitopes on the enzymes glycogen phosphorylase and sulphite oxidase, respectively. To test this, preparations of these two enzymes were applied in ELISA and immunoblotting, and the reactivities of sera from large groups of well-defined PBC patients (and other chronic liver disease patients) were studied. No specific reactivity with either putative antigen was observed in ELISA nor immunoblotting. However, with both antigens a positive correlation was observed between ELISA optical density readings and serum IgG levels in both the PBC and chronic liver disease groups which suggests some non-specific binding of immunoglobulin to the proteins. We conclude that antimitochondrial antibodies (AMA) do not specifically recognise glycogen phosphorylase and sulphite oxidase and the use of these antigens to determine the 'AMA profile' and indicate prognosis is not valid.