A new antimitochondria antibody (anti-M6) in iproniazid-induced hepatitis.

A new immunofluorescence pattern of non-organ- and non-species-specific antibody has been observed in occasional sera. Variations of the fluorescence were found in different species. Recognition of the new pattern was particularly characteristic in rat organs (liver: the hepatocytes showed intense roughly granular fluorescence evenly distributed in the cytoplasm; kidney: the bright fluorescence of the first portion of the proximal tubules contrasted with the negative aspect of the other portions of the tubules; stomach: only some cells probably corresponding to the APUD system were positive; pancreas: fluorescence was limited to the islets of Langherhans). The positivity in the ellipsoid region of the rods and cones of the eye and the absorption on different liver organelles showed that this aspect corresponded to the mitochondria. We propose to name this pattern 'antimitochondria antibody number 6' or 'anti-M6'. High titres of anti-M6 were found in four patients suffering from iproniazid-induced hepatitis. A decrease in the titre was obtained after stopping the treatment. The now exceptional use of iproniazid and the rare occurrence of anti-M6 suggest a link between these two phenomena.