IgA autoantibodies against human eye muscle antigen detected by western blotting and immunohistochemical methods in Graves' disease

Graves' orbitopathy: extraocular muscle/total orbit area ratio is positively related to the Clinical Activity Score

BACKGROUND AND OBJECTIVE

Both extraocular muscle (EOM) and orbital fat are involved in Graves' orbitopathy (GO) but their enlargement might occur with a different temporal pattern. Two GO subtypes have been described, one with predominant EOM enlargement and the other with prevalent fat tissue involvement. We longitudinally investigated the EOM in patients with GO and their relationship with clinical activity.

PATIENTS AND METHODS

By using commercial software with a segmentation technique, we calculated from computed tomography (CT) scan EOM coronal area (CA) and total orbit coronal area (TOA) in 23 control subjects and in 32 patients with GO. The latter were studied both at presentation and 18 months later. Superior, lateral, inferior, and medial EOM areas and TOA were selected by 3 different contiguous CT slices: A, B, and C, chosen at globe pole tangent and 2 and 4 mm backward. The Clinical Activity Score (CAS) was also measured.

RESULTS

Orbital EOM CA/TOA ratio (OM/TOA ratio) after 18 months decreased in most patients with GO, indicating that EOM area decrement contributed significantly to OM/TOA ratio reduction. Clinical Activity Score decrease was significantly correlated to the OM/TOA ratio decrease.

CONCLUSIONS

An easy method to measure CA of EOM and orbit allowed us to observe that in most patients with GO the OM/TOA ratio decreases with time, suggesting that macroscopic EOM involvement occurs initially and resolves as the other clinical signs and symptoms of the disease resolve, as indicated by the significant OM/TOA ratio correlation with CAS.

Autoantibodies to novel membrane and cytosolic antigens of the lachrymal gland in primary Sjögren's syndrome

Sjögren's syndrome (SS) is a prototypical systemic autoimmune disease, where autoimmune processes lead to the dysfunction of the exocrine glands. The key feature of the disease is autoimmune exocrinopathy, causing reduced tear secretion and subsequent keratoconjunctivitis sicca (KCS). The aim of this study was to investigate the connection between the presence of autoantibodies to lachrymal gland antigens and the reduced tear production in patients with primary SS. Ninety-nine patients, 90 women and 9 men, were investigated in the study. Twenty healthy young women served as controls. Enzyme-linked immunosorbent assay (ELISA) and Western blotting were applied to detect autoantibodies to antigen fractions prepared from the human lachrymal gland membrane and cytosolic fractions. Autoantibodies of the IgG, IgA and IgM isotypes to the lachrymal membrane and cytosolic fractions were detected in about one third (27%) of the patients with primary SS. IgA antobodies to the membrane and cytosolic fractions occurred most frequently in SS patients. A significant difference was found in the presence of IgA antibodies to the membrane lachrymal fraction between patients and controls given in ELISA indices (1.23 +/- 0.3 vs 1 +/- 0.19, p < 0.001). IgG, IgA, and IgM isotypes of autoantibodies directed to the membrane lachrymal fraction of 200-180, 120-116, 80-70, 58, 50, 48.5, 40 and 28.8 kDa were also identified in patients. Membrane IgG antibody levels showed a positive correlation (R = 0.998; p = 0.045) with the clinical loss of secretory function (Schirmer's test values). Positive correlation was found between membrane IgM and anti-SS-A levels (R = 0.962; p = 0.038) and also between cytosolic IgM antibodies and anti-SS-A levels (R = 0.982; p = 0.018). IgG, IgA and IgM types of autoantibodies may play a role in the development of the impaired lachrymal secretion and therefore may be involved in the pathogenesis of KCS.

Immunohistochemical studies using immunized Guinea pig sera with features of anti-human thyroid, eye and skeletal antibody and Graves' sera

Type 2 5' deiodinase enzyme was observed in both thyroid and eye muscle tissues, highlighting its possible role as a common antigen in thyroid-associated ophthalmopathy. Sera of 105 Graves' patients and 40 controls, and immunized guinea pig sera against TCSS peptide, showing homology to the amino acid sequence from 132 to 152 of type 2 5' deiodinase, were investigated to demonstrate the binding effects to human thyroid, eye and skeletal muscle tissues. Twenty-two Graves' patients were positive for anti-TCSS peptide antibodies, of whom 18 cases had ophthalmopathy. The levels of anti-TCSS peptide antibodies were higher not only in Graves' patients with (P<0.0001) and without (P<0.036) eye symptoms compared to controls but also the difference was significant between patients with and without ophthalmopathy (P<0.049). In Western blot, immunized sera showed binding reactions to the supernatant fractions of human thyroid, eye and skeletal muscle tissues at the range of 29 kDa. Patient sera with Graves' ophthalmopathy resulted in positive reactions directed to membrane areas in thyroid follicular cells, and to fibers in eye and skeletal muscles using immunohistochemical method, while no positive staining was present after adding control sera. The binding features of immunized guinea pig sera exhibited similar staining in all human tissues but could be blocked with Graves' sera. Our results suggest that type 2 5' deiodinase enzyme protein could play a role as an antigen in Graves' disease. Immunized guinea pig sera against TCSS peptide exhibited similar binding reactions and stainings to human thyroid, eye and skeletal muscle tissues as patient sera with Graves' ophthalmopathy.

Eye muscle antibodies in Graves' ophthalmopathy: pathogenic or secondary epiphenomenon?

The extra ocular (eye) muscles are one of the principal tissues involved in the autoimmune-mediated inflammation of Graves' ophthalmopathy (GO). Several eye muscle proteins are targeted by autoantibodies or sensitized T lymphocytes, or both, and include: G2s, which is now identified as the terminal 141 amino acids of the winged-helix transcription factor FOXP1, the flavoprotein (Fp) subunit of the mitochondrial enzyme succinate dehydrogenase, the so-called "64kDa protein", a non-tissue specific membrane protein called 1D and the calcium binding protein calsequestrin. Of these, antibodies against G2s and Fp are the most sensitive markers of eye muscle damage in patients with thyroid autoimmunity even though neither antigen is specific to eye muscle and neither antibody is specific to GO. However, the recent finding that the calsequestrin gene is 4.7 times more expressed in eye muscles than other skeletal muscles suggests that we should reconsider the possible role of anti-calsequestrin autoantibodies in ophthalmopathy. GO may comprise two main subtypes with different pathogenetic mechanisms, namely ocular myopathy in which eye muscle inflammation predominates and congestive ophthalmopathy where inflammatory changes occur in the periorbital connective tissues in the absence of eye muscle dysfunction. Anti-G2s and anti-Fp antibodies are closely associated with the ocular myopathy subtype of GO while antibodies targeting type XIII collagen, the only member of the collagen family to have a transmembrane domain, are closely linked to congestive ophthalmopathy. Since both G2s and Fp are intracellular antigens it is unlikely that either antibody causes eye muscle fiber damage in GO, although a role in the later stages of the disease when the fiber has released its cellular contents has not been excluded. Eye muscle antibodies that are cytotoxic to eye muscle cells in antibody-dependent cell-mediated cytotoxicity (ADCC) are more likely to play a role in eye muscle fiber damage since they target a putative eye muscle cell membrane antigen, the identity of which is currently being investigated. While anti-G2s and anti-Fp antibodies are probably secondary to an underlying reaction, such as cytotoxic T lymphocyte targeting of an eye muscle membrane antigen that has yet to be identified, they are reliable markers of immunologically mediated eye muscle fiber damage in patients with Graves' hyperthyroidism. In conclusion, while a pathogenic role for eye muscle antibodies has not been excluded, they are most likely secondary to cytotoxic T cell reactions in GO and, as such, good markers of this autoimmune disease.

Soluble CD4 concentrations predict relapse of post-partum thyroiditis

Post-partum thyroiditis (PPT) is a common autoimmune thyroid disorder which results in significant morbidity at a critical time of a woman's life. The presence of anti-thyroglobulin (anti-TG) and, more so, anti-thryroperoxidase (anti-TPO) antibodies in the first trimester of pregnancy has been reported to forecast subsequent PPT. Despite their predictive value, these tests lack in specificity. We have sought to find an alternative that is more specific and, ideally, which could be tested immediately proximate to the event. We have taken advantage of the high recurrence rate of PPT in subsequent pregnancies to perform a prospective study of serum soluble CD4 (sCD4) and CD8 (sCD8) levels in 22 pregnant women who had at least one previous episode of PPT. This group was matched with 21 pregnant women of comparable age with no evidence of thyroid disease. Both groups of women were sampled in each of the three trimesters of pregnancy, 1 month, 3 months and 6 months post-partum for sCD4, sCD8, thyroid function parameters and antibodies. Twelve of the 22 women with previous PPT had recurrent disease; they were more likely to be cigarette smokers and to have a family history of autoimmune disorders (p<0.05, for both) than those who did not. Half of these women had high anti-TG or anti-TPO each in the first trimester compared to none among those without recurrent PPT and 2/21 controls. Serum sCD8 levels showed no changes over the observation points among the two PPT patient subsets and were comparable to those of the controls. By contrast, serum sCD4 concentrations showed divergent changes in the group with recurrent PPT in the course of pregnancy and postpartum period compared to those without disease recurrence and controls: sCD4 failed to show the physiological fall in the third trimester of pregnancy [19.0+/-1.7 (+/-SD) U/ml vs 15.6+/-2.3 U/ml in controls, NS]. This trend was continued into the first month post-partum when sCD4 levels were clearly higher than in controls (22.1+/-2.6 U/ml compared to 17.9+/-1.9 U/ml in controls, p<0.001) and well before the episode of PPT. An sCD4 serum level outside the 95% reference range at 1 month post-partum (9/12 in recurrent PPT, 1/21 in controls) yields a relative risk of 6.9 (chi2=14.67, p<0.001) compared to 3.3 for first trimester thyroid antibody positivity (p=0.029). In summary, we describe a reliable test for forecasting PPT that can be obtained immediately proximate to the possible event. If our findings are verified in larger studies, the measurement of serum sCD4 concentration drawn in the first month post-partum may prove an ideal test for population screening for impending PPT.

Management of Graves' ophthalmopathy: reality and perspectives

Graves' ophthalmopathy is an debilitating disease impairing the quality of life of affected individuals. Despite recent progress in the understanding of its pathogenesis, treatment is often not satisfactory. In mild cases, local therapeutic measures (artificial tears and ointments, sunglasses, nocturnal taping of the eyes, prisms) can control symptoms and signs. In severe forms of the disease (3-5%), aggressive measures are required. If the disease is active, high-dose glucocorticoids and/or orbital radiotherapy, or orbital decompression represent the mainstay of treatment. If the disease is severe but inactive, orbital decompression is preferred. Novel treatments such as somatostatin analogs or intravenous immunoglobulins are under evaluation. Rehabilitative (extraocular muscle or eyelid) surgery is often needed after treatment and inactivation of eye disease. Correction of both hyper- and hypothyroidism is crucial for the ophthalmopathy. Antithyroid drugs and thyroidectomy do not influence the course of the ophthalmopathy, whereas radioiodine treatment may cause the progression of preexisting ophthalmopathy, especially in smokers. The exacerbation, however, is prevented by glucocorticoids. In addition, thyroid ablation may prove beneficial for the ophthalmopathy in view of the pathogenetic model relating eye disease to autoimmune reactions directed against antigens shared by the thyroid and the orbit.

Beneficial effect of pentoxifylline on thyroid associated ophthalmopathy (TAO)*: a pilot study

We have previously found that pentoxifylline (Ptx) inhibited cytokine induced HLA-DR expression and glycosaminoglycan (GAG) synthesis by retroorbital fibroblasts. We have now tested the clinical efficacy of Ptx in treating TAO. Ten patients with moderately severe ophthalmopathy were selected for study. All patients were euthyroid before and during the 12 weeks of the Ptx therapy. Serum GAG, TNF-alpha, anti-TSH-receptor, anti-eye muscle, anti-thyroglobulin and anti-thyroid peroxidase antibodies were determined sequentially. At the end of 12 weeks eight of the ten patients showed improvement in soft tissue but not in proptosis or extraocular muscle involvement. At baseline the levels of GAG (5.2+/-0.92 mg/dl v.s. 0.7+/-0.14 mg/dl, p<0.001) and TNF-alpha (33.6+/-6.6 pg/ml v.s. 5.4+/-1.3 pg/ml, p<0.001) were increased in patients compared to controls. They gradually decreased in the eight patients who responded to Ptx: after 4, 8 and 12 weeks of therapy serum GAG was 3.4+/-0.42 mg/dl, 2.5+/-0.77 mg/dl (p<0.01) and 1.1+/-0.2 mg/dl (p<0.001), respectively and serum TNF-alpha was 20.9+/-4.8 pg/ml, 14.9+/-2.2 pg/ml (p<0.05) and 9.7+/-1.8 pg/ml (p<0.01), respectively. Serum GAG and TNF alpha did not fall in the two patients who did not respond. The titre of anti-eye muscle antibodies but not anti-thyroid antibodies were lower at 12 weeks. Ptx has a beneficial effect on inflammatory symptoms of TAO and associated laboratory parameters in the majority of patients.

High circulating IL-6 level in Graves' ophthalmopathy

IL-6 is a paracrine and autocrine cytokine, which acts in the regulation of immunological and inflammatory processes. Its production can be observed in different cell types, as well as thyrocytes. The purpose of the study was to examine the serum IL-6 levels between the patients with Graves' disease (N = 47) and without (N = 29) ophthalmopathy in respect of the presence of inflammatory eye signs and thyroiditis, thyroid function and radioiodine or medical treatments. The serum IL-6 levels were greater (P < 0.025) in the patients with ophthalmopathy (440 +/- 32.4 pg/ml) than in those without eye disease (81.6 +/- 25.2 pg/ml). An elevated serum IL-6 levels could be detected in 22 out of 47 patients with ophthalmopathy with longer manifestation of thyroid disease than one year in comparison with those who had shorter (694 +/- 35.3 pg/ml vs 215.8 +/- 27.9 pg/ml, P < 0.05). The increase showed a strong association with the inflammatory signs of eye disease in the patients with Graves' hyperthyroidism compared with those without ophthalmopathy (513.3 +/- 33.7 pg/ml vs 96.9 +/- 12.1 pg/ml, P < 0.025). Euthyroid function and the presence of thyroiditis did not influence the serum IL-6 levels. Radioiodine and medical treatments did not lead to a remarkable decrease in the serum IL-6 levels. The results supported that IL-6 cytokine may be an important factor in the inflammatory events of Graves' ophthalmopathy.