The thyroid-stimulating antibody of Graves' disease: evidence for restricted heterogeneity.

The thyroid-stimulating antibody (TSAb) of Graves' disease was shown to have a relatively constant pH on preparative isoelectric focusing; the fraction of pH 8.5-9.0 was maximal in thyroid-stimulating potency but inhibition of thyrotropin-binding (another property of Graves' disease IgG) was most marked with pH 9.5-10.6 fraction. H and L chains of TSAb-IgG were separated and H original (HO) was combined with L original (LO) and with Bence Jones L kappa and L lambda. Only HO + LO restored (minimal) bioactivity. Of isolated TSAb-IgG kappa and TSAb-IgG lambda only IgG lambda was thyroid stimulating. Sub-classes (IgG3 and IgG 1 + 2 + 4) of TSAb-IgG were prepared and with all of 6 sera TSAb was in IgG 1 + 2 + 4 with none in IgG3. These data combine to suggest heterogeneity of this autoimmune antibody.