Decrease in acetylcholine-receptor content of human myotube cultures mediated by monoclonal antibodies to alpha, beta and gamma subunits.

One of the two main causes of acetylcholine-receptor loss in myasthenia gravis is antigenic modulation, i.e. accelerated internalization and degradation rate by antibody-crosslinking. This phenomenon has been studied only in animal tissues. Therefore, we tested antigenic modulation of the acetylcholine receptor on human embryonic myotubes in cultures. Several monoclonal antibodies to the alpha, beta and gamma subunits of the receptor reduced its concentration, in some cases down to one-third of the control. Some of these antibodies only form complexes of one antibody with two receptor molecules; consequently such small complexes are sufficient to accelerate internalization of the human acetylcholine receptor. This technique might be proved valuable for clinical screening of sera from myasthenic patients.