Enhancement of growth of allogeneic mouse tumor by the IgG1 fraction of alloantibody preparations.

Because staphylococcal protein A binds all the known subclasses of mouse IgG except IgG1, ethanol-fixed staphylococci were used as an adsorbent to prepare IgG1 fractions of anti-BALB/c alloantibody-containing globulins and normal globulins of the same strains. The loss of more than 99% of the IgG2 as a result of this adsorption was demonstrated by immunodiffusion. The IgG1 fractions of C3H and CBA anti-BALB/c globulins were tested for their effect on growth of the BALB/c plasmacytomas MOPC-315 and MOPC-460 in C3H and CBA mice by incubation with the tumor cells before transplantation and by injection periodically thereafter into the hosts. With alloantibody-containing globulins that showed slight enhancement of growth of these tumors, or none, the IgG1 preparations caused considerable enhancement of tumor growth. Control preparations of normal C3H or CBA globulins, or IgG1 fractions similarly prepared from the normal globulins, showed no enhancing effect on the growth of these tumors.