Release of low molecular weight proteins from the Fc fragment of rabbit immunoglobulin G induced by formation of insoluble complexes with antigen.

Serum rabbit IgG was found to be in complexes, with low mol. wt proteins (mol. wt about 1500) which are noncovalently associated with the Fc fragment. The formation of precipitating antigen-antibody complexes resulted in the dissociation of IgG complexes with these proteins and their release in solution. On formation of non-precipitating antigen-antibody complexes, the dissociation of low mol. wt proteins from IgG was not observed.