[The phenomenon of double line of IgG in immunoelectrophoresis (author's transl)].

Immunoelectrophoretic studies of patients' sera occasionally reveal a parallel splitting of the IgG precipitation line if the test is performed with polyvalent antihuman antiserum directed not only against the Fc-part of the IgG molecule. This phenomenon has been studied in a patient with discoid lupus erythematosus and another patient with lymphadenopathy of unknown origin. Apparently, this finding was not due to a monoclonal gammopathy: In the cellulose membrane electrophoresis no extragradient could be observed and assays with antisera directed against free and bound light chains showed a regular pattern. The splitting of the IgG precipitate is much rather caused by polyclonal IgG with a high proportion of slowly diffusing heterogenous IgG-x, as has been found in studies using the immunoelectrophoresis as well as the analytical ultracentrifuge. It was not due to Fab fragments.