Anti-microsomal antibody (AMA) activity was inhibited in 14 of 16 sera and in all 12
IgG preparations from patients with
postpartum thyroiditis following incubation with F(ab')2 fragments from normal polyspecific
immunoglobulin for
therapeutic use (
ivIg). Similar results were observed with sera from seven of seven patients with
Graves' disease and five of six patients with
autoimmune hypothyroidism. Results of these competitive binding assays and affinity chromatography of AMA
IgG on
Sepharose-bound F(ab'), fragments from
ivIg indicated that AMA
antibodies reacted with
ivIg through idiotypic-anti-idiotypic interactions. Eight out of 10
IgG preparations from patients with autoimmune
thyroid disease also showed inhibition of AMA activity when coincubated with autologous
IgM at various
IgG:
IgM molar ratios. These observations suggest that
ivIg can inhibit anti-microsomal
antibodies through idiotype-anti-idiotype interactions and that such interactions occur with
IgM anti-idiotype antibodies in vivo, providing evidence of a role for idiotypic network regulation in the control of thyroid autoimmunity.