[Subclasses of immunoglobulin G. I. Determination of subclasses of G-paraproteins by the method of tryptic splitting].

Subclasses of the G-paraproteins were examined by the method of tryptic splitting of the sera. The fragments were identified in the immunoelectrophoresis with the antisera detecting the IgG, Fab-, Fc- and Fc1-fragments. It was revealed that for the IgGI most typical was formation of the Fc1-fragment continuously detected along with the Fab- and Fc-fragments; for the IgG1--retention of a considerable amount of unsplit protein; for the IgG3--formation of the Fab- and Fc-fragments, for the IgG4-- of the Fab-fragment alone. Analysis of 96 sera of the patients suffering from G-myeloma showed that 69 were referred to the IgGl, 19 - to the IgG2, 5 - to the IgG3, and 3 - to the IgG4. The method tested permitted successful identification of subclasses of the G-paraproteins, this serving as the necessary prerequisite for the choice of antigens and sorbents in the preparation of the subclass-specific antisera.