Receptors, antibodies, and disease

Abnormal antibody production is now recognized as the basis of specific endocrine and neurological diseases and their complications. Among the autoimmune diseases, the best understood from a mechanistic point of view are myasthenia gravis, Graves' disease, several variants of insulin resistance, and a variant of bronchial asthma. In each of these human disorders, the clinical symptoms can be traced to the actions of antireceptor antibodies produced by a deranged immune system. The autoantibodies produced in these diseases are functionally heterogeneous. They may produce the clinical symptoms of hormone or neurotransmitter insufficiency either by blocking the binding of these agents to target cell surface receptors or by accelerating the internalization and degradation of these receptors. In other cases, the autoantibodies may produce the clinical signs of hormone excess by mimicking the actions of the hormone, in an uncontrollable fashion. In some cases, functionally different types of autoantibodies will appear in the same patient at different stages of the disease. For all of these autoantibodies, of whatever function, assays for their presence in serum are available, in forms suitable for clinical chemists, as well as for researchers; these will be described in this review. In addition to the known anti-receptor autoimmune diseases, there are a large number of other autoimmune diseases for which there is fragmentary evidence that their clinical symptoms have an anti-receptor autoantibody etiology. Several examples of this group will be discussed, and assays suitable for establishing the presence of anti-receptor antibodies in the sera of such patients will be provided. The disorders to be considered are: type I diabetes mellitus, chronic atrophic gastritis, autoimmune Addison's disease, autoimmune hypoparathyroidism, type II pseudohypoparathyroidism, resistant ovary syndrome, connective tissue diseases, and the HLA-B8/DR3 antigen haplotype as a potential marker for autoimmune diseases of the anti-receptor type.