The role of apoptosis in thyroid autoimmunity

Thyroid autoimmunity and its association with cellular and humoral immunity in women with reproductive failures

PROBLEM

thyroid autoimmunity (TAI), which is T helper (Th)1-cell-mediated autoimmunity to thyrocytes, is associated with increased risk of miscarriages and highly prevalent in women with infertility. We aim at investigating the prevalence of TAI in women with recurrent spontaneous abortions (RSA) or unexplained infertility (UI) and its relationship with cellular and humoral immune abnormalities.

METHOD OF STUDY

prevalence of antiphospholipid antibodies, anti-nuclear antibody, other non-organ-specific antibodies (NOSAs; anti-dsDNA, anti-ssDNA, anti-histone, anti-Scl70), peripheral blood natural killer (NK) cell levels (%) and cytotoxicity, and CD3(+) /CD4(+) Th1/Th2 cell ratios were compared in women with and without TAI. Thyroid functional tests (TFT) were analyzed in both groups before and after pregnancy.

RESULTS

tumor necrosis factor-α/IL-10 expressing CD3(+) /CD4(+) cell ratios (P < 0.05), CD56(+) NK cell levels (P < 0.05), the prevalence of anticardiolipin antibodies (P < 0.05) and other NOSAs (P < 0.005) were significantly higher in women with TAI when compared to women without TAI. Changes in thyroid-stimulating hormone levels between before and after pregnancy in women with TAI were significantly higher when compared to those of women without TAI (P < 0.05).

CONCLUSION

TAI is associated with impaired cellular and humoral immune responses in women with RSA or UI. In women with TAI, serial TFT is recommended when pregnancy is established.

Prevalence and functional significance of thyrotropin receptor blocking antibodies in children and adolescents with chronic lymphocytic thyroiditis

CONTEXT

TSH receptor (TSHR) blocking antibodies (Abs) inhibit TSH-induced thyroid growth and function in some adults with chronic lymphocytic thyroiditis (CLT), but their role in the pediatric age range is unknown.

OBJECTIVES

Our objectives were: 1) to determine the prevalence of TSHR blocking Abs in children and adolescents with CLT and 2) assess their functional significance both in vivo and in vitro.

DESIGN AND SETTING

This was a retrospective study in a referral outpatient setting.

PATIENTS

Sera from a total of 87 CLT patients and 33 controls were studied.

MAIN OUTCOME MEASURES

TSHR Abs were measured by both ELISA and bioassay.

RESULTS

Eight of 87 children and adolescents with CLT (9.2%), including one as young as 4 yr of age, had TSHR Abs in serum as measured by ELISA. The prevalence was significantly higher in individuals whose serum TSH concentration was 20 mU/liter or greater within 3 months of study than in less hypothyroid patients (eight of 45 vs. none of 42, P < 0.005). Conversely, TSHR Ab-positive patients were significantly more hypothyroid at diagnosis but only when the analysis was restricted to those with severe hypothyroidism was a decreased prevalence of goiter observed. IgG purified from TSHR Ab sera retained the TSH binding-inhibitory activity and TSHR Ab-positive sera inhibited TSH-induced stimulation of cAMP significantly more than normal.

CONCLUSIONS

TSHR-blocking Abs contribute significantly to the severity of the hypothyroidism in some children with CLT, but as compared with adults, they appear to play less of a role in determining the presence or absence of a goiter.

Autoimmune thyroid disease: unlocking a complex puzzle

PURPOSE OF REVIEW

The autoimmune thyroid diseases (AITD), Graves' disease and chronic lymphocytic thyroiditis (CLT) are amongst the most common endocrine diseases in childhood and adolescence. The application of molecular biology has permitted an unparalleled insight into susceptibility genes that predispose to their development and has allowed enhanced understanding of their complex immune pathophysiology.

RECENT FINDINGS

The susceptibility genes that predispose to AITD can be subdivided into those that affect the immune response in general and thyroid-specific antigens. Both known and new susceptibility genes have been the focus of recent attention. Although there is no known human leukocyte antigen (HLA) association in CLT, recent work has demonstrated an association with a specific amino acid pocket signature irrespective of the HLA-DR class. In Graves' disease a specific combination of polymorphisms for thyroglobulin and HLA-DR markedly increases the odds ratio for developing disease. The availability of recombinant antigen [particularly thyroid peroxidase and thyrotropin (TSH) receptor] and of high affinity monoclonal antibodies has provided insight into the specific epitopes recognized by antibodies in AITD and has confirmed the increased affinity of stimulating TSH receptor antibodies for the shed A subunit rather than the holoreceptor.

SUMMARY

Powerful molecular tools have been developed that have shed light on the nature of the susceptibility genes for and the pathophysiology of AITD. These have already led to improved diagnostic tools and, hopefully, will permit the development of more specific immune therapy in the future.

Influence of signal transducer and activator of transcription-1 signaling on thyroid morphology and function

Interferon (IFN)-gamma has been involved in the pathogenesis of Hashimoto thyroiditis. It is a cytokine released by infiltrating mononuclear cells that mediates its actions mainly through signal transducer and activator of transcription-1 (STAT1) but also through other transcription factors. To dissect the effect of IFN gamma on thyroid morphology and function, we crossed transgenic mice that express IFN gamma specifically in the thyroid gland to mice deficient in STAT1. Lack of STAT1 ameliorated the abnormal thyroid morphology and the primary hypothyroidism typical of IFN gamma transgenic mice but not the suppressed iodine accumulation. Interestingly, lack of STAT1 alone decreased iodine accumulation, seemingly through expression of TGFbeta. These results indicate that STAT1 is required to mediate some but not all of the phenotypic changes induced by IFN gamma and that it also regulates iodine accumulation via TGFbeta signaling.

[Spontaneous hypothyroidism in 4 patients with Graves-Basedow disease]

We present 4 patients with Graves' disease who developed spontaneous hypothyroidism during follow-up. The two most plausible physiopathologic mechanisms for this development were progressive autoimmune-mediated destruction of the thyroid follicular epithelium and a predominance of blocking antibodies to the thyroid-stimulating hormone (TSH) receptor at the expense of stimulating antibodies in the same patient. Description of these patients not only illustrates the heterogeneous nature of this disease, but also the interrelation among its distinct clinical forms.

Persistent infection of a carcinoma thyroid cell line with coxsackievirus B

BACKGROUND

Viral infections are described as environmental factors that are implicated in various thyroid diseases. The role of enteroviruses (EV) in the pathogenesis of thyroid diseases has been suspected. Recently, we found that EV RNA could be detected in postoperative thyroid specimens. We decided to investigate the infection of a human thyroid cell line with coxsackievirus B4 (CVB4).

METHODS

The wild-type human thyroid carcinoma cells K1 were inoculated with CVB4E2 at 2.1 x 10(7) TCID50/mL. The titer of the virus progeny was determined every 3 days on HEp-2 cells. CVB replication at the molecular level was monitored by searching for intracellular viral genomes using reverse transcription (RT)-polymerase chain reaction (PCR). EV VP1 capsid protein was detected by indirect immunocytofluorescence staining. Cell viability was determined by 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) absorbance, and the nuclear morphology was assessed by Hoechst Dye staining.

RESULTS

Infectivity assays with CVB4E2 revealed an increase in viral titers. Virus production decreased thereafter, but was not stopped by serial subculture for 24 days after infection. Detection of intracellular positive and negative viral RNA strands by RT-PCR was positive between days 1 and 14 postinfection (p.i.), and by semi-nested RT-PCR up to 24 days. K1 cell cultures infected with CVB4 were stained positively for EV VP1: the number of VP1-positive cells decreased rapidly within 6 days and remained low up to the end of culture. Compared with mock-infected cultures, viability in CVB4-infected cultures was around 100% up to 24 days. Cells with strongly fluorescent nuclei and/or fragmented nuclei were observed.

CONCLUSION

We demonstrate for the first time that CVB4 could replicate in thyroid cells and could persist, with predominance of viral negative RNA strands for up to 24 days p.i. without obvious cytopathic effect. Our results suggest that CVB4 may lead to thyroid cell apoptosis. Further studies are needed to determine whether CVB could play a role in thyroid pathologies.

The relationship between thyroid function, serum monokine induced by interferon gamma and soluble interleukin-2 receptor in thyroid autoimmune diseases

Interactions between cytokines play an important role in the development of thyroid autoimmunity. Using enzyme-linked immunosorbent assay we investigated serum concentrations of soluble interleukin-2 receptor (sIL-2R), interferon-gamma, tumour necrosis factor (TNF)-alpha, interleukin (IL)-10, CD30, monokine induced by interferon-gamma (MIG), cytotoxic T lymphocyte antigen-4 and markers of apoptosis decoy receptor 3 and Bcl-2 in 28 patients with hyperthyroid Graves' disease (GD), 24 patients with untreated Hashimoto's thyroiditis (HT) and 15 healthy controls. TNF-alpha, IL-10 and sIL-2R were higher in GD compared with HT and controls (TNF-alpha: 8.79 in GD versus 2.54 pg/ml in HT, P = 0.01; IL-10: 10.00 versus 3.10 versus 3.10 pg/ml, P(1) < 0.001, P(2) = 0.005; sIL-2R: 1.26 versus 0.64 versus 0.46 ng/ml, P < 0.001). MIG and CD30 were higher in HT compared with controls (649.22 +/- 262.55 versus 312.95 +/- 143.35 pg/ml, P = 0.037, 6.57 +/- 2.35 versus 3.03 +/- 1.04 U/ml, P = 0.036 respectively). In GD sIL-2R decreased when the euthyroid state was achieved (1.31 +/- 0.64 versus 0.260 +/- 0.11, n = 12, P < 0.001). sIL-2R correlated positively with free thyroxine (FT4) (R = 0.521, P = 0.000) and negatively with thyroid stimulating hormone (TSH) (R = -0.472, P = 0.00132). MIG correlated negatively with FT4 (R = -0.573, P = 0.00234) and positively with TSH (R = 0.462, P = 0.0179). The results suggest that serum concentrations of sIL-2R and MIG are related to thyroid function rather than to activation of autoimmunity.

Patogênese das doenças tiroidianas autoimunes

A doença tiroidiana autoimune (DAIT), que afeta de 2% a 5% da população ocidental, é o transtorno autoimune órgão-específico mais comum. Sua apresentação clínica varia do hipertiroidismo da doença de Graves (DG) ao hipotiroidismo associado à tiroidite de Hashimoto (TH). A exata etiologia da DAIT permanece desconhecida, mas a interação entre suscetibilidade genética e fatores ambientais desencadeadores parece ser de fundamental importância no seu desenvolvimento. Postula-se que fatores genéticos responderiam por 79% da suscetibilidade à DAIT e os ambientais por 21%. Genes imunomoduladores, como o complexo maior de histocompatibilidade (MHC), antígeno-4 associado ao linfócito T citotóxico (CTLA-4), a molécula CD40 e a proteína tirosina fosfatase-22 (PTPN22) e os genes específicos da glândula tiróide, como receptor do TSH (TSHR) e tiroglobulina (TG) têm sido identificados. A natureza exata do envolvimento do meio ambiente no desenvolvimento da DAIT não é bem conhecida, mas vários fatores ambientais têm sido envolvidos, como o conteúdo de iodo na dieta, estresse, drogas e infecções. Entretanto, não há evidência clara de causalidade e os mecanismos pelos quais fatores ambientais desencadeariam a autoimunidade tiroidiana, em indivíduos geneticamente predispostos, ainda permanecem não completamente entendidos. O conhecimento dos mecanismos precisos de interação entre fatores ambientais e genes na indução da autoimunidade tiroidiana poderia resultar desenvolvimento de novas estratégias de prevenção e tratamento.

Epigenetics and human disease

Changes to covalent modifications of DNA and histones can be induced via environmental stimuli such as nutrients, hormones and drugs. These changes can be both transient and heritable in nature and provide a framework in which to investigate how environment and lifestyle choices impact disease susceptibility and progression. Furthermore, these modifications are central to chromatin dynamics and, as such, play key roles in many biological processes involving chromatin, such as DNA replication and repair, transcription and development. In this review we provide an overview of recent advances in our understanding of the roles that DNA and histone modification play in the onset and progression of human disease.

The consequences of apoptosis in autoimmunity

The clearance of apoptotic cells is a highly regulated mechanism, normally associated with anti-inflammatory response. During early stages of apoptosis the cell is promptly recognized and engulfed by professional phagocytes or tissue cells to avoid the outflow of intracellular content and limit the immunological reaction against released antigens. However, increasing evidences suggest that impairment in the uptake of apoptotic cell debris is linked to the development of autoimmunity. In fact, autoantigens have been demonstrated to be content within apoptotic bodies and apoptotic cells seems to be critical in the presentation of antigens, activation of innate immunity and regulation of macrophage cytokine secretion. We herein review the known mechanisms for regulating the uptake of the products of apoptosis in the development of autoimmunity.