Binding of gamma-globulin fragments to muscle tissue.

Serum γ-globulins from normal persons and from twenty-four patients with myasthenia gravis were tested in the antiglobulin consumption test before and after pepsin digestion. F(ab') fragments prepared from normal sera did not bind to muscle tissue, while Fc fragments did. Accordingly, muscle binding γ-globulins from normal sera bind to the tissue only by the Fc portion of the molecule. F(ab') preparations from sera from patients with myasthenia gravis combined with the tissue. In twelve of these sera, the amount of muscle binding γ-globulin was shown to be quantitatively within normal limits. The difference in binding capacity registered between the different patient sera is quantitative, while the data indicate a qualitative difference between normal and patient sera.