Secretor status and infection in patients with Graves' disease

Graves' disease: Epidemiology, genetic and environmental risk factors and viruses

Graves' disease (GD) is the most common cause of hyperthyroidism in developed Countries. It is more common between 30 and 60 years; 5-10 times more frequent in women. The genetic predisposition accounts for 79% of the risk for GD, while environmental factors for 21%. About 70% of genes associated with autoimmune thyroid disorders (AITD) are implicated in T-cell function. Among GD endogenous factors, estrogens, X-inactivation and microchimerism are important. Among environmental risk factors, smoking, iodine excess, selenium and vitamin D deficiency, and the occupational exposure to Agent Orange have been associated with GD. Many studies showed that HCV is associated with thyroid autoimmunity and hypothyroidism, in patients with chronic HCV hepatitis (CHC); a significant link has been shown also between HCV-related mixed cryoglobulinemia and risk for GD. Moreover, IFN-α-treated CHC patients develop GD more frequently. Novel studies are needed about possible risk factors to reduce the occurence of GD in West Countries.

The microbiota and autoimmunity: Their role in thyroid autoimmune diseases

Since the 1970s, the role of infectious diseases in the pathogenesis of Graves' disease (GD) has been an object of intensive research. The last decade has witnessed many studies on Yersinia enterocolitica, Helicobacter pylori and other bacterial organisms and their potential impact on GD. Retrospective, prospective and molecular binding studies have been performed with contrary outcomes. Until now it is not clear whether bacterial infections can trigger autoimmune thyroid disease. Common risk factors for GD (gender, smoking, stress, and pregnancy) reveal profound changes in the bacterial communities of the gut compared to that of healthy controls but a pathogenetic link between GD and dysbiosis has not yet been fully elucidated. Conventional bacterial culture, in vitro models, next generation and high-throughput DNA sequencing are applicable methods to assess the impact of bacteria in disease onset and development. Further studies on the involvement of bacteria in GD are needed and may contribute to the understanding of pathogenetic processes. This review will examine available evidence on the subject.

Role of genetic and non-genetic factors in the etiology of Graves' disease

In spite of the advancements in understanding the pathogenic mechanisms of Graves' disease (GD), its ultimate cause remains elusive. The majority of investigators agree that GD is likely a multifactorial disease, due to a complex interplay of genetic and non-genetic factors that lead to the loss of immune tolerance to thyroid antigens and to the initiation of a sustained autoimmune reaction. Twin and family studies support a role of genetic factors, among which the HLA complex, CD40, CTLA-4, PTPN22, FCRL3, thyroglobulin, and the TSH receptor may be involved. Among non-genetic factors, iodine, infections, psychological stress, gender, smoking, thyroid damage, vitamin D, selenium, immune modulating agents, and periods of immune reconstitution may contribute the development of the diseases. Here we review in detail the respective role of genetic and non-genetic factors in the etiology of GD, taking advantage of the great bulk of data generated especially over the past 30 years.

Neonatal hyperthyroidism associated with isolated submandibular sialadenitis: is it just a coincidence?

Isolated submandibular sialadenitis is extremely rare in the neonatal period. All reported cases had predisposing factors such as prematurity, dehydration, anatomic deformities, calculi, and long-term oro-gastric tube feeding. Here, we present a case of neonatal isolated submandibular sialadenitis without any known risk factors and who was diagnosed later with hyperthyroidism secondary to maternal Graves' disease. Both sialadenitis and hyperthyroidism resolved with appropriate treatment. While both conditions are rare and important in neonatal emergency care, the possibility of neonatal hyperthyroidism should be explored in cases with isolated sialadenitis if there is no other risk factor. Possible mechanisms for this uncommon association are discussed.

Current perspective on the pathogenesis of Graves' disease and ophthalmopathy

Graves' disease (GD) is a very common autoimmune disorder of the thyroid in which stimulatory antibodies bind to the thyrotropin receptor and activate glandular function, resulting in hyperthyroidism. In addition, some patients with GD develop localized manifestations including ophthalmopathy (GO) and dermopathy. Since the cloning of the receptor cDNA, significant progress has been made in understanding the structure-function relationship of the receptor, which has been discussed in a number of earlier reviews. In this paper, we have focused our discussion on studies related to the molecular mechanisms of the disease pathogenesis and the development of animal models for GD. It has become apparent that multiple factors contribute to the etiology of GD, including host genetic as well as environmental factors. Studies in experimental animals indicate that GD is a slowly progressing disease that involves activation and recruitment of thyrotropin receptor-specific T and B cells. This activation eventually results in the production of stimulatory antibodies that can cause hyperthyroidism. Similarly, significant new insights have been gained in our understanding of GO that occurs in a subset of patients with GD. As in GD, both environmental and genetic factors play important roles in the development of GO. Although a number of putative ocular autoantigens have been identified, their role in the pathogenesis of GO awaits confirmation. Extensive analyses of orbital tissues obtained from patients with GO have provided a clearer understanding of the roles of T and B cells, cytokines and chemokines, and various ocular tissues including ocular muscles and fibroblasts. Equally impressive is the progress made in understanding why connective tissues of the orbit and the skin in GO are singled out for activation and undergo extensive remodeling. Results to date indicate that fibroblasts can act as sentinel cells and initiate lymphocyte recruitment and tissue remodeling. Moreover, these fibroblasts can be readily activated by Ig in the sera of patients with GD, suggesting a central role for them in the pathogenesis. Collectively, recent studies have led to a better understanding of the pathogenesis of GD and GO and have opened up potential new avenues for developing novel treatments for GD and GO.

Increased natural autoantibody activity to cytoskeleton proteins in sera from patients with necrobiosis lipoidica, with or without insulin-dependent diabetes mellitus

Necrobiosis lipoidica (NL), a skin disease, is associated with insulin-dependent diabetes mellitus (IDDM). Natural autoantibody (NAb) activity in sera from 16 patients suffering from NL, with or without IDDM, was compared to that in sera from 41 patients with IDDM and 43 healthy controls. Isotype-specific enzyme-linked immunosorbent assays (ELISAs) were used to detect NAbs against actin, myosin, keratin, desmin, troponin, tropomyosin, thyroglobulin, insulin, single-stranded DNA and the hapten trinitrophenyl. NAb activity was significantly higher in sera from patients with NL (either with or without IDDM), compared with that detected in sera from patients with IDDM which was similar to that of healthy individuals. High proportion of NL sera exhibited increased IgG anti-tropomyosin (69%), anti-troponin, anti-desmin and anti-keratin (50% each), anti-insulin (44%) and anti-trinitrophenyl (31%) activities, as well as increased IgA and IgM anti-keratin activities (26% and 31%, respectively). The great majority (88%) of positive sera were polyreactive and contained NAbs, polyspecific and monospecific (as demonstrated by immunoadsorption studies), belonging to more than one isotype; there was no predominant serological reactivity pattern. In conclusion, increased NAb activity to cytoskeleton proteins is associated with the dermatological disease NL and not to the overlapping autoimmune disease (IDDM). The origin and significance of these NAbs is discussed.

Seroreactivity to bacterial antigens is not a unique phenomenon in patients with autoimmune thyroid diseases in Canada

It has been suggested elsewhere that the enteric pathogen Yersinia enterocolitica (Y.e.) might be implicated etiologically in autoimmune thyroid disease (AITD). To reevaluate this hypothesis in the Canadian population, where the prevalence of anti-Y.e. antibodies in the general population is very low (< 1%), we have studied the occurrence of antibacterial reactivity (against Y.e. 0:3 and 0:9, Escherichia coli and Staphylococcus aureus) in the sera of patients with Hashimoto's thyroiditis (HT), Graves' disease (GD), nontoxic nodular goiter (NTG), and autoimmune rheumatic diseases (ARD) as well as normal controls (C). Using the tube agglutination method, no single positive sample was detected in these subjects. No differences in the mean levels of anti-Y.e. 0:3 or 0:9 by ELISA were observed between various groups of patients. Immunoreactivity in the course of medical therapy during 5-12 months did not show significant changes in any of 12 ARD and AITD patients. Some serological reactivity to the plasmid containing strain of Y.e. 0:3 was demonstrated in all subjects by the Western blotting technique. However, weaker signals and fewer bands were noticed in these sera compared to sera from patients with acute yersiniosis. Analysis of the pattern of reactivity did not show any difference in reactivity to any protein between the groups of subjects. The immunodominant antigen in Y.e. 0:3 to which IgG reacted in almost all subjects was the plasmid encoded 240-kDa protein. Our study favors the view that there is a merely coincidental incidence of seroreactivity to bacterial antigens, which appears to be irrespective of diagnosis.

AB0 and Lewis blood groups in reactive arthritis

In this study we evaluated secretor status in patients with reactive arthritis. Previous evidence indicates that non-secretion of AB0 and Lewis blood group antigens to saliva and other secretions is associated with susceptibility to certain bacterial infections and certain diseases with suspected autoimmune etiology. Secretor status can be determined based on the Lewis phenotype. We studied AB0, Lewis and Rhesus blood groups of 54 patients with previous reactive arthritis, 26 of whom had uroarthritis and 28 of whom had arthritis after enteric infection. Furthermore, 25 patients with uncomplicated yersiniosis and 57 healthy controls were studied. We did not find any correlation between secretor status and reactive arthritis or gastroenteritis due to Yersinia. AB0 blood group antigen B appeared to be protective against uroarthritis.