We studied 32 patients with idiopathic hypoparathyroidism (IHP), 19 patients with organ-specific autoimmune diseases (OSAD) without IHP, 50 normal controls and a known serum with anti-mitochondrial autoantibodies (AMA). Patients' sera were tested by the classical indirect immunofluorescent technique and by the indirect immunofluorescent complement fixation technique on unfixed cryostat sections of normal human parathyroid, pancreas, thyroid, stomach, kidney, and rat kidney. Five out of 32 patients with IHP, three out of 19 patients with OSAD without IHP and one out of 50 normal controls revealed a bright reactivity against oxyphil cells and a weak reactivity against chief cells of normal parathyroid. These sera also brightly reacted with mitochondria-rich cells and weakly with the remaining cells of only human tissues. The absorption of positive sera with human mitochondria completely abolished this positivity but the absorption with rat mitochondria failed to prevent this reaction. This reactivity was due to an anti-human mitochondrial autoantibody (AHMA) of IgG class. By non-competitive ELISA and Western blot we also demonstrated that every AHMA-positive serum mainly reacted against a human mitochondrial membrane-bound protein of approximate mol. wt. of 46 kd, while the AMA-positive serum reacted against different mitochondrial antigens. The present study shows that a specific parathyroid autoantibody was not detectable in patients with IHP.
