The Cardiac Auto-Immune System

Abstract

(1) The properties of the 5 cardiac antigens in human heart which cross-react with rabbit anti-rabbit heart auto-antibodies were studied, and compared to the rabbit heart auto-antigens analyzed previously. They were found to be similar in many respects. All were rendered undetectable by proteinases, but were unaffected by ribonuclease or desoxyribonuclease; they were salted out by exposure to similar concentrations of ammonium sulfate or potassium phosphate; they were variably labile to heat or pH extremes; and their elution characteristics from hydroxyl apatite and Sephadex G-100 were similar. (2) Further evidence was obtained that the human cardiac proteins detectable with rabbit anti-rabbit heart auto-antibodies were found <i>only</i> in human heart, and were not present in human skeletal muscle, kidney, pancreas, liver or plasma. (3) Passive hemagglutination assay correlated with immunodiffusion tests in terms of organ specificity and auto-antibody titers. (4) The precipitin systems formed between rabbit anti-rabbit heart auto-antibodies and human heart extracts failed to show esterase, catalase, glucosaminidase, glucuronidase, cysteine-amino-peptidase or phosphatase activities, as had been found earlier for the rabbit heart auto-immune system. Cardiolipin was found to be unrelated to any of the above human cardiac auto-antigens. (5) Urea, with or without dithiothreitol, incactivated only 2 of the human cardiac auto-antigens.