Comparison of antibody titer to human and rat acetylcholine receptor in myasthenia gravis

Antibody titer to acetylcholine receptor (AChR Ab) was measured in 34 patients with myasthenia gravis (MG) using an immunoprecipitation method with human and rat AChR as antigens, to study the reliability of these assay systems and the cross-reactivity between human and rat AChR. There was a good correlation in the titer of Ab to AChR between human and rat (P< 0.01) when Ab titers were expressed logarithmically. The titer of Ab to human AChR was higher in a group of patients with a high concentration of AChR Ab and lower in a group with a low concentration of AChR Ab than that to rat AChR. This indicates that there may be distinctive characteristics in AChR Ab between groups of patients with high and low concentrations of AChR Ab.