Immune complex deposits in thyroid glands of patients with Graves' disease: I. Complement system in serum and thyroid gland of patients with Graves' disease

Circadian Clock and Complement Immune System-Complementary Control of Physiology and Pathology?

Mammalian species contain an internal circadian (i.e., 24-h) clock that is synchronized to the day and night cycles. Large epidemiological studies, which are supported by carefully controlled studies in numerous species, support the idea that chronic disruption of our circadian cycles results in a number of health issues, including obesity and diabetes, defective immune response, and cancer. Here we focus specifically on the role of the complement immune system and its relationship to the internal circadian clock system. While still an incompletely understood area, there is evidence that dysregulated proinflammatory cytokines, complement factors, and oxidative stress can be induced by circadian disruption and that these may feed back into the oscillator at the level of circadian gene regulation. Such a feedback cycle may contribute to impaired host immune response against pathogenic insults. The complement immune system including its activated anaphylatoxins, C3a and C5a, not only facilitate innate and adaptive immune response in chemotaxis and phagocytosis, but they can also amplify chronic inflammation in the host organism. Consequent development of autoimmune disorders, and metabolic diseases associated with additional environmental insults that activate complement can in severe cases, lead to accelerated tissue dysfunction, fibrosis, and ultimately organ failure. Because several promising complement-targeted therapeutics to block uncontrolled complement activation and treat autoimmune diseases are in various phases of clinical trials, understanding fully the circadian properties of the complement system, and the reciprocal regulation by these two systems could greatly improve patient treatment in the long term.

Neutrophils from Brazilian patients with Graves' disease: some biochemical and functional aspects

Graves' disease shows important systemic inflammatory complications and has been considered to be systemic autoimmune thyroid, skeletal muscle and connective tissue syndrome. Neutrophils participate in the pathophysiology of the two major immune and inflammatory manifestations of the disease, ophthalmopathy and myxedema, and may worsen the inflammatory picture. In this study we analysed some biochemical and functional aspects of neutrophils in Graves' disease patients to assess their participation in these processes. The results show that the complement and/or Fcgamma receptor-mediated oxygen radical production by neutrophils was increased when patient cells were compared with controls. However the percentage of cells expressing complement and IgG receptors and the per-cell fluorescence, were similar, indicating that the increased oxidative burst was not due to an abnormal expression of mediating receptors. The production of hydrogen peroxide was also increased in hyperthyroid patient neutrophils as compared to controls. Conversely, antioxidant defences (superoxide dismutase activity and reduced glutathione content) in neutrophils from patients were not significantly different from healthy controls. The liberation of potent oxidative compounds together with the absence of adequate quenching of them by antioxidant mechanisms could be responsible for greater tissue damage in inflammatory conditions, as is the case in ophthalmopathy and myxedema patients. Considering our results and those of other workers, we encourage and suggest an associated antioxidant therapy to complement the conventional anti-thyroid therapy, especially in obvious inflammatory cases and in individuals who smoke.

Autoimmune thyroid disease: immunological, pathological, and clinical aspects

Autoimmune thyroiditis, most notably Hashimoto's thyroiditis, appears to be increasing in prevalence and is now more easily detected by sensitive laboratory tests and more invasive procedures such as fine needle aspiration. During the last decade, marked progress has been made in the understanding of these diseases. There is a greater awareness of the interaction between the humoral and cell-mediated arms of the immune system in autoimmune thyroiditis. Recent studies implicate a subpopulation of suppressor T lymphocytes which have an antigen-specific defect, resulting in their suboptimal interaction with the helper T lymphocytes and subsequent autoimmune manifestations. There is some evidence that thyroid epithelial cells which inappropriately express HLA-DR may enhance presentation of thyroid antigens to the immune system, possibly significant in the initiation or enhancement of the autoimmune response. The presence of various antithyroid autoantibodies allows the use of laboratory assays to confirm the clinical diagnosis and predict the results of treatment. There appears to be predisposing genetic factors in the development of autoimmune thyroiditis, with some geographical and racial differences. Environmental factors, most notably dietary intake of iodine, have also been implicated in the pathogenesis of Hashimoto's thyroiditis. Several animal models have been developed addressing such issues. Ongoing studies in the areas of postpartum thyroiditis and childhood thyroiditis are helpful in clarifying their relationship with Hashimoto's thyroiditis. Graves' disease and postpartum thyroiditis are being investigated as possible causes of postpartum depression. The association of Hashimoto's thyroiditis and carcinoma of the thyroid gland is still controversial, but its relationship with malignant lymphoma is now well accepted. Thus, although the pathogenesis of autoimmune thyroiditis remains elusive, there has been significant refinement of the clinical diagnosis, and immunological abnormalities of specific intrathyroidal lymphocytes have been identified. Hopefully, these new areas of knowledge will assist in the treatment of these diseases and in the prevention of the development of malignant lymphomas of the thyroid gland.

Immunohistochemical study of intrathyroidal lymph follicles

Tissue samples from 76 cases of thyroid disease containing germinal centers (GCs) were selected from 396 cases of various thyroid diseases for immunohistochemical analysis of the GC and follicular dendritic cell (FDC). These 76 cases included 28 cases of thyroid cancer, 23 of chronic thyroiditis, 12 of nontoxic goiter, 8 of adenoma, and 5 of Graves' disease. In many lymphoid GCs IgG, IgM and kappa and lambda light chains were detected with a lacy dendritic pattern. Only thyroglobulin (Tg), among the various thyroid-associated antigens sought, was stained in GCs and was found in the same distribution as immunoglobulins. Tg was found in all of the disease categories studied. Moreover, early components in the classical complement (C) pathway, that is, C1q, C4, C3c, C3d, and C5, were detected in almost all GCs in the thyroid tissues in a lacy dendritic pattern. C3d was intensely positive and was seen also by immunoelectron microscopy on the cell surface of FDCs. It is concluded that not only immunoglobulins but also Tg and early C components are closely related to the GC and FDC in the intrathyroidal lymph follicle.

Immunological features of endemic goiter

Some immune aspects of simple endemic goiter have been studied through a comparison of IgG, IgA, IgM, kappa and lambda chains, and C3 and C4 in the peripheral blood of 59 patients operated on for goiter and the peripheral blood of 49 normal controls. The median IgM was lower in the goiter blood. The incidence of thyroglobulin (Tg) and microsomal (Mi) antibodies (Abs) was 20.3% in goiter blood and that of nonthyroid autoAbs was 37%. Active and total rosetted blood lymphocytes were counted and OKT3, OKT4, OKT8, Leu 1, Leu3a, Leu2b, T DR+, and NK cell populations were classified. Helper T cells were occasionally decreased when goiter was associated with lymphocytic thyroiditis. The NK percentage was sometimes higher in goiter blood, whereas the T DR+ percentage was not significantly different in the two groups. Lymphocyte infiltration (LI) was noted in 32% of goiters (about 5% with a diffuse and nodular pattern). A prevalence of helper/inducer cells was observed among the infiltrating T cells. HLA-DR antigen (Ag) positive epithelial cells were seen, not only in LI areas. Granular deposits of IgG, IgA, IgM, and C3 on the follicular basal membrane were stained in 6.7% of goiters Patterns histologically and immunologically similar to those in Hashimoto's thyroiditis may therefore be observed in long-standing simple endemic goiter, suggesting that an autoimmune mechanism may be involved in its pathogenesis.