The antigenic and immunosuppressive properties of normal and antilymphocytic equine IgG subfractions.

The antigenic and immunosuppressive properties of normal and antilympho-cytic equine globulin subfractions were investigated in the rat model in an attempt to increase the efficacy of prolonged ALG therapy by limiting the immunogenic stimulus of `inactive' subfractions. Chromatographic separation of equine IgG components yielded an electro-phoretically slow gamma 2 fraction consisting of IgG2a and IgG2b and a more heterogeneous fast gamma 1 subfraction. Immunosuppression resulting from the administration of isolated subfractions was measured by the response to alum-BSA and skin allograft survival. Antigenicity was determined by a variety of immunological procedures. The immunosuppressive character of the ALG was confined to the gamma 2 fraction, however this fraction also proved antigenic in our system. The administration of normal equine IgG subfractions in combination with Freund's complete adjuvant resulted in the demonstration of antigenic differences between the fast and slow IgG components.