Antibody response after alloimmunization with heart tissue in the rat. Characterization of the autoantibodies

LEW antisera to DA heart homogenate or DA vascularized allografts were studied using 125I anti-immunoglobulin binding assays with heart homogenate as the target tissue. In this way, the full spectrum of antibodies generated could be studied. In both sera, the main antibody generated was autoantibody directed at antigens found in highest concentration in heart tissue. These autoantibodies were readily demonstrated in binding assays using heart homogenate as target, but were not detected in binding or cytotoxicity assays with lymphocyte suspensions as targets. Immunofluorescence studies showed that the autoantibody response was complex. The autoantibodies in the antihomogenate serum were strong and were directed primarily at intracellular components found in the myocardial cells, the bases of the tubular cells in the kidney, and type I skeletal muscle fibers, and were possibly directed at mitochondria. The antigraft serum was weaker and contained, in addition to the putative antimitochondrial autoantibodies, autoantibodies directed at the intercalated discs. In addition, a component of the antibodies was directed at alloantigens and this is discussed in the succeeding paper.