Evidence for the cell-surface localization of antigens cross-reacting with the "mitochondrial antibodies" of primary biliary cirrhosis.
Studies with subfractions of Saccharomyces cerevisiae obtained by differential centrifugation showed only two primary biliary cirrhosis-specific antigens. These antigenic species were shown, using preabsorption studies, to have determinants cross-reactive with their mammalian counterpart. Distribution profiles of marker enzymes and primary biliary cirrhosis antigens between sucrose density gradient subcellular fractions of yeast showed that a relatively high concentration of primary biliary cirrhosis-specific antigens was associated with fractions containing plasma membranes, as well as those containing mitochondria. The possible cell-surface localization of the primary biliary cirrhosis antigens was further investigated using an indirect immunofluorescent technique on a number of different mammalian cells. Rat hepatoma cells, isolated rat hepatocytes and human polymorphonuclear leukocytes and lymphocytes stained positively with primary biliary cirrhosis sera, but not with normal sera or primary biliary cirrhosis sera preabsorbed with beef heart mitochondria. However, blood cells from primary biliary cirrhotic patients gave positive immunofluorescence in all tests, which is compatible with prior binding of the patients' own antimitochondrial antibodies to the surface of the cells.