alpha-Bungarotoxin displacing antibody in myasthenia gravis

The majority of sera from myasthenic patients cannot precipitate all available receptor-toxin complex even in conditions of a 4,000-fold excess of antibody. This effect was traced to displacement of toxin from the receptor-toxin complex. Pure IgG prepared from the serum of a myasthenic patient was as effective as the original serum in displacing ability. The possible effect of such antibodies on the correlation of antibody titre and disease state is discussed.