Glycosaminoglycan antibodies in endocrine ophthalmopathy

Thyrotropin receptor antibodies and Graves' orbitopathy

CONTEXT AND PURPOSE

The thyrotropin receptor (TSHR) is the key autoantigen in Graves' disease (GD) and associated orbitopathy (GO). Antibodies targeting the TSHR (TSHR-Ab) impact the pathogenesis and the course of GO. This review discusses the role and clinical relevance of TSHR-Ab in GO.

METHODS

Review of the current and pertinent literature.

RESULTS

GO is the most common extrathyroidal manifestation of GD and is caused by persistent, unregulated stimulation of TSHR-expressing orbital target cells (e.g. fibroblasts and pre-adipocytes). Serum TSHR-Ab and more specifically, the stimulatory Ab (TSAb) are observed in the vast majority of patients with GD and GO. TSHR-Ab are a sensitive serological parameter for the differential diagnosis of GO. TSHR-Ab can be detected either with conventional binding immunoassays that measure binding of Ab to the TSHR or with cell-based bioassays that provide information on their functional activity and potency. Knowledge of the biological activity and not simply the presence or absence of TSHR-Ab has relevant clinical implications e.g. predicting de-novo development or exacerbation of pre-existing GO. TSAb are specific biomarkers of GD/GO and responsible for many of its clinical manifestations. TSAb strongly correlate with the clinical activity and clinical severity of GO. Further, the magnitude of TSAb indicates the onset and acuity of sight-threatening GO (optic neuropathy). Baseline serum values of TSAb and especially dilution analysis of TSAb significantly differentiate between thyroidal GD only versus GD + GO.

CONCLUSION

Measurement of functional TSHR-Ab, especially TSAb, is clinically relevant for the differential diagnosis and management of GO.

Immunologically active autoantigens: the role of toll-like receptors in the development of chronic inflammatory disease

Pattern recognition receptors (PRRs), expressed on cells of both the innate and adaptive immune systems, serve as sentinels, waiting to alert the host to the first signs of microbial infection and to activate the initial line of immune defense. Research has increasingly demonstrated that many of the same PRRs also recognize self-epitopes that either are released from dying or damaged cells or are present at the surface of apoptotic cells or apoptotic bodies. In this context, PRRs play a critical role in tissue repair and the clearance of cellular debris. However, failure to appropriately regulate self-responses triggered by certain PRRs can have serious pathological consequences. The Toll-like receptor (TLR) gene family represents a case in point. TLR7, 8, and 9 were originally identified as receptors specific for bacterial and viral RNA and DNA, but more recent in vitro and in vivo studies have now linked these receptors to the detection of host RNA, DNA, and RNA- or DNA-associated proteins. In this context, they likely play a key role in the development of systemic autoimmune diseases.

A Sick Eye in a Sick Body? Systemic Findings in Patients with Primary Open-angle Glaucoma

Despite intense research, the pathogenesis of primary open-angle glaucoma (POAG) is still not completely understood. There is ample evidence for a pathophysiological role of elevated intraocular pressure; however, several systemic factors may influence onset and progression of the disease. Systemic peculiarities found in POAG include alterations of the cardiovascular system, autonomic nervous system, immune system, as well as endocrinological, psychological, and sleep disturbances. An association between POAG and other neurodegenerative diseases, such as Alzheimer disease and Parkinson disease, has also been described. Furthermore, the diagnosis of glaucoma can affect the patient's quality of life. By highlighting the systemic alterations found in POAG, this review attempts to bring glaucoma into a broader medical context.

Solid phase assays in glycoconjugate research: applications to the analysis of proteoglycans, glycosaminoglycans and metalloproteinases

Glycoconjugates are a class of macromolecules consisting of different constituents, one of which is sugar moieties. Glycoconjugates comprise the majority of tissue constituents, both intracellular and extracellular. Extracellular glycoconjugates (glycoproteins and proteoglycans) participate in a wide variety of interactions, through which they maintain tissue integrity. Therefore, their analysis or the study of their possible interactions would give evidence for the state of tissues. Since the amounts of some of the extracellular glycoconjugates are usually low or the amounts of tissue to be examined come from biopsies, specific analytical systems are developed for their study, the most familiar being solid phase assays, which have the advantages of analysis of multiple samples on the same time, cheap instrumentation and high specificity.

Antibodies to chondroitin sulfates A, B, and C: clinico-pathological correlates in neurological diseases

Anti-chondroitin sulfates (ChSs) antibodies have been reported in neuropathy and neurodegenerative diseases. Differences in specificities may account for their association with different diseases. Sera from 303 neurological patients were tested for antibodies to ChSs A, B, C. Titers >/=51,200 were found in 16 patients (eight peripheral neuropathy, three motor neuron disease, four multiple sclerosis, one myelitis). Three patients also had anti-sulfatides antibodies, which in two cases cross-reacted with ChSs. By indirect immunofluorescence, positive sera stained nuclei on normal human peripheral nerve sections. These findings indicate that human anti-ChSs antibodies are broadly reactive and not specific to any neurological disease.

Glycosaminoglycans in thyroid eye disease

Orbital accumulation of hydrophilic, interstitial glycosaminoglycans (GAG) and subsequent expansion of retrobulbar tissue lead to the clinical manifestation of exophthalmos in patients with thyroid eye disease (TED). In order to analyze whether the alteration of distribution pattern and biochemical composition of GAG and proteoglycans play a role in the development of the disease, a highly specific high-pressure liquid chromatography (HPLC) method was developed. The concentration of total GAG, chondroitin sulfate A (CA), dermatan sulfate (DS), and hyaluronic acid (HA) was determined in patients and controls, revealing marked differences in urinary concentration of total GAG and HA, as well as an elevation of CA in patients versus controls. Method sensitivity was 0.86 for patients with active disease, and 0.87 for patients with untreated ophthalmopathy, whereas specificity was 1.0 for patients with inactive disease. Patients with increased GAG concentration responded well to steroids and/or orbital irradiation. Furthermore, distribution pattern of orbital extracellular matrix GAG exhibited a significant increase in the tissue fractions of CA and HA in patients with TED in comparison to controls. In conclusion, GAG polysaccharides not only play a major role in the pathogenesis of TED but have been successfully introduced as an activity marker of the disease.