Thyrotropin binding and long acting thyroid stimulator absorbing activities in subcellular fractions from isolated thyroid cells and thyroid homogenates.

The ability of various thyroid subcellular fractions to bind [125I]iodo TSH and to absorb long-acting thyroid stimulator (LATS) and thyroid stimulating immunoglobulins (TSI) activities was examined. Membranes purified from thyroid homogenates or isolated thyroid cells absorbed LATS/TSI activities and specifically bound [125I]iodo TSH. Purified thyroglobulin, nuclei, mitochondria and ribosomes did not bind [125I]iodo TSH nor did they absorb LATS/TSI activities. Cell sap obtained by gentle lysis of isolated thyroid cells failed to absorb LATS/TSI activities and to bind labeled hormone. However, freeze-thawing of the cells fragmented the membranes, releasing [125I]iodo TSH binding as well as LATS/TSI absorbing activities into the soluble (cell sap) fraction. The results suggest that the LATS/TSI antigen is of cell surface origin, includes the TSH receptor or larger membrane fragments containing the receptor, and that its release into the soluble fraction is due to the fragmentation of the thyroid membrane during homogenization and preparative procedures.

The spectrum and significance of autoantibodies reacting with the thyrotropin receptor.

Autoantibodies that occur in autoimmune thyroid disease and that interact with the TSH receptor are reviewed. Current limited understanding of the nature of the TSH receptor is detailed, and available assays for the different types of antibodies are described. The incidence, clinical significance, and interactions of the various antibodies are summarized.

[Autoimmune thrombocytopenia and diffuse-toxic goiter]. / Autoimmunnaia trombotsitopeniia i diffuzno-toksicheskii zob.

The authors describe 10 patients with associated diffuse toxic goiter and thrombocytopenic purpura and a female patient with associated goiter and a three-shoot autoimmune peripheral cytopenia. In 8 patients thyrotoxicosis preceded the appearance of thrombocytopenia, in 3 patients, both the conditions were diagnosed at a time. In 4 patients, the measurements were taken of the IgG content on the surface of platelets according to Dixon et al. In 3 patients, the IgG content turned out to be appreciably elevated, in one patient, the content of IgG was within normal, however the latter patient was examined after prednisolone intake that had given rise to an increase in the platelet count. Two patients who received radioactive iodine and three patients treated by thyrostatic drugs were later on subjected to splenectomy. In 4 patients, thrombocytopenic purpura remitted after subtotal strumectomy. One female patient was subjected to sectoral resection of the thyroid. Two years after surgery the patient, who was in an euthyroid state, developed thrombocytopenia which required splenectomy. It is possible that in the latter case there was no direct relation between the two diseases. The relationship between the two autoimmune diseases, diffuse toxic goiter and thrombocytopenic purpura, remained unclear in other 10 cases. The relationship between the diseases under consideration and approaches to specifying the character of such a relationship are under discussion.

[Myxedema tuberosum atypicum (Jadassohn-Doesserkker, 1916) in the clinical picture of the myxodermias and in the normal course of Graves-Basedow's disease]. / O myxedema tuberosum atypicum (Jadassohn-Doesserkker, 1916) no quadro das mixodermias e no ciclo formal da moléstia de Graves-Basedow.

An extraordinary case: large cutaneous tumors, intense "endocrine" exophthalmos, macroglossia, acropachie, prétibial mucinosis, diffuse myxodermia, symptoms of systemic involvement.

Immunological studies on LATS-immunogloblin by the reaction with staphylococcal protein A.

The reaction of LATS activity with Staphylococcal Protein A, a specific binding protein with the Fc part of human IgG(1), IgG(2) and Ig(4), was examined. When IgG(1), IgG(2) and Ig(4) subclasses were removed from LATS positive sera or LATS-IgG fractions by affinity chromatography on Protein A-Sepharose, LATS activity decreased. Almost all LATS activity was found in the fraction that reacted with Protein A. It is suggested that LATS has an expression of a very distinct immunoglobulin G structure, and that LATS activity is distributed mainly in the fraction containing IgG(1), Ig(2) and Ig(4) in LATS positive serum;

Distribution of LATS activity in immunoglobulin G subclass.

The immunological character of LATS was examined by affinity chromatography on Anti-IgG, Anti-Fab, Anti-Fc and Staphylococcal Protein A bound Sepharose. By affinity chromatography on Anti-IgG, Anti-Fab and Anti-Fc bound Sepharose, it is possible to separate LATS-immunoglobulin from LATS positive serum without loss of activity. Affinity chromatography on Protein A bound Sepharose is useful for obtaining further purified LATS-immunoglobulin. By this method, it is possible to separate IgG molecules of the subclasses IgG(1), IgG(2) and IgG(4) with high LATS activity. LATS activity was not found in the IgG(3) fraction. When IgG(1) fraction was purified from the fraction containing the 3 subclasses of IgG(1), IgG(2) and IgG(4), about 85% of total protein was found in IgG(1). However, specific activity per protein of LATS in IgG(1) fraction did not change remarkably. After papain hydrolysis the thyroid stimulating activity of LATS-immunoglobulin was located in Fab fraction of these 3 subclasses of IgG(1), IgG(2) and IgG(4), and especially in IgG(1). The Fab fraction presents a short acting type of thyroid stimulating activity. These data indicate that LATS activity is mainly distributed in the Fab fragment of IgG(1).

Comparison of LATS activity and TSH receptor antibody in Graves' disease.

TSH-receptor antibody (TRAb) activity and LATS activity of Graves' sera were compared. All of 50 LATS-positive cases were TRAb positive, although only 63% of LATS-negative cases were TRAb positive. Binding of 125I-TSH to the TSH receptors was inhibited dose-dependently by LATS-immunoglobulin. However, no correlation between TRAb activity and LATS activity was observed. TRAb was positive in 2 LATS-positive cases even when the symptoms of hyperthyroidism were controlled by treatment (antithyroid or radioisotope). The positive TRAb was not changed in 4 Graves' disease patients whose LATS activity had disappeared following antithyroid treatment. These clinical studies show that TRAb is more sensitive than LATS and suggest that LATS may be one of a heterogenous population of antibodies to the TSH receptor in Graves' disease.

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.

Graves' ophthalmopathy.

Graves' ophthalmopathy usually occurs in association with hyperthyroidism. Its occasional occurrence in the absence of thyroid disease suggests, however, that it may be a separate autoimmune disorder. While the evidence supporting an autoimmune pathogenesis is considerable for the ophthalmopathy, it is not so impressive as that for Graves' hyperthyroidism: orbital antibodies have not been convincingly demonstrated and autoantigens have not been identified. On the other hand, in patients with Graves' ophthalmopathy the orbital tissues and eye muscle membranes are infiltrated with lymphoid cells and show evidence of cell-mediated immune reactions. Although there is some evidence that binding of thyroid stimulating hormone fragments and thyroglobulin-antithyroglobulin immune complexes to eye muscle membranes may be important in the pathogenesis of the ophthalmopathy, this needs to be confirmed. The mechanism for the association of hyperthyroidism and ophthalmopathy is unknown, but the association likely reflects an influence of thyroid hormones on the immune system. In view of the autoimmune pathogenesis the logical treatment of Graves' ophthalmopathy appears to be immunosuppression.