Abstract
The thyroid-stimulating antibody (TSAb) of Graves'' disease has 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. 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. Restricted heterogeneity of this autoimmune antibody is suggested.