Acetylcholine Receptor-Ab (ARAb) Blocking Radioimmunoassay

Radio immuno assay for the quantitative determination of blocking autoantibodies against the acetylcholine receptor in human serum. The ARAb Blocking RIA is useful as an aid in the differential diagnosis of myasthenia gravis (MG). Myasthenia gravis (MG) is an acquired disorder of neuromuscular transmission associated with abnormal muscle weakness and fatigabilities on exertion. This muscle weakness increases with muscle activity, eventually reaching a state of pseudoparalysis. After muscle relaxation the motility is restored. Muscles that are required for body posture, including facial and neck muscles as well as ocular muscles and muscles needed for speaking and swallowing are most affected. Clinical symptoms may be restricted to one muscle group, in particular the eye muscles (ocular MG) or become generalized (generalized MG). Myasthenia gravis can occur from early childhood to old age and its prevalence is about 5 per 100,000. In women, the disease usually presents between the ages of 20 to 40, whereas in men the age of presentation tends to be between 40 and 60 years. The incidence of MG is 40 to 60 new cases per million people per year. Autoantibodies directed against acetylcholine receptors along the postsynaptic membrane are responsible for the muscle weakness and fatigabilities in MG. Three functionally different types of antibodies against acetylcholine receptors are detectable in patients with MG: receptor binding, blocking and modulating antibodies. Related to the blocking antibodies there is a significant correlation between the degree of acetylcholine receptor blockade and generalization of muscle weakness. Therefore, measurement of blocking acetylcholine receptor autoantibodies is of additional value in differential diagnosis of MG.