Variations in the levels of IgG1 and IgG2 subclasses in the sera of normal, immunized and tumor-bearing hamsters.

The concentration of IgG1 and IgG2 subclasses in the sera of hamsters bearing tumors of different origins were compared to that of normal serum and to that of sera of animals rendered resistant to tumor take by immunization with viable SV40-transformed cells. In the sera of hamsters bearing tumors induced by virus-transformed cells an augmentation of IgG2 and a diminution of IgG1 was observed during the development of the tumor compared to sera of normal hamsters. In the sera of animals bearing tumors induced by methylcholanthrene ( MCH2 ) or by spontaneously transformed cells ( EHB ) the level of IgG2 was almost normal but IgG1 was barely detectable, especially in MCH2 tumors. On the other hand, the sera of animals immunized with virus-transformed cells showed a slight increase in both IgGs, but only that of IgG2 was significant. Antibody activity was tested in the sera as well as in the IgG1 and IgG2 fractions of the sera of hamsters immunized or bearing tumors induced by SV40 transformed cells. Both sera and the subclasses showed antibody activity, the activity being more pronounced in the IgG2 fraction than in the IgG1 fraction.