Heterogeneity of the antibody response to thyroglobulin: effects of 6-mercaptopurine.

Treatment with 6-mercaptopurine delayed synthesis of both IgG and IgM anti-thyroglobulin antibodies after primary immunization. Synthesis of IgG, but not IgM, was inhibited. A third Ig, of β mobility, was detected during the secondary response and appeared to be inhibited in the rabbits treated with 6-mercaptopurine during both the primary and secondary responses. Homocytotropic antibody activity was only slightly affected by 6-mercaptopurine treatment. Treatment with 6-mercaptopurine during both the primary and secondary responses had relatively little effect on the magnitude of the secondary response, although higher levels of precipitating antibody were observed for rabbits treated with 6-mercaptopurine during only the primary response. These results suggest caution in the extrapolation of the experimental results obtained with 6-mercaptopurine (and perhaps other metabolic inhibitors) to diverse experimental systems.