Passive immunity to murine plasmacytoma by rabbit antiidiotypic antibody to myeloma protein.

Antiidiotypic antisera to LPC-1 and MOPC-300 plasmacytoma globulins were produced in rabbits by immunization with the corresponding antigen and exhaustive immunoabsorption with normal BALB/c plasma and other myeloma globulins. IgG fractions of these antisera when given intraperitoneally on three consecutive days after tumor implantation, protected the animal specifically from the grafting of the corresponding plasmacytoma or induced regression of the tumors after their initial grafting and growth. In vitro cytotoxicity of the antisera to plasmacytoma cells was not demonstrated. Plasma of the antisera-treated normal BALB/c mice, though containing antiidiotypic antibody in high titers (320-640), was not cytotoxic to tumor cells. The inhibitory effect on tumor growth can be considered the result of passive immunization against plasmacytoma with xenogeneic humoral antibody.