Fetal microchimeric cells in autoimmune thyroid diseases: harmful, beneficial or innocent for the thyroid gland?

Molecular Mechanisms in Autoimmune Thyroid Disease

The most common cause of acquired thyroid dysfunction is autoimmune thyroid disease, which is an organ-specific autoimmune disease with two presentation phenotypes: hyperthyroidism (Graves-Basedow disease) and hypothyroidism (Hashimoto’s thyroiditis). Hashimoto’s thyroiditis is distinguished by the presence of autoantibodies against thyroid peroxidase and thyroglobulin. Meanwhile, autoantibodies against the TSH receptor have been found in Graves-Basedow disease. Numerous susceptibility genes, as well as epigenetic and environmental factors, contribute to the pathogenesis of both diseases. This review summarizes the most common genetic, epigenetic, and environmental mechanisms involved in autoimmune thyroid disease.

A review on the effect of prolyl isomerization on immune response aberration and hypersensitivity reactions: A unifying hypothesis

Little is known about the causes and mechanisms of ectopic immune responses, including different types of hypersensitivity, superantigens, and cytokine storms. Two of the most questionable phenomena observed in immunology are why the intensity and extent of immune responses to different antigens are different, and why some self-antigens are attacked as foreign. The secondary structure of the peptides involved in the immune system, such as the epitope-paratope interfaces plays a pivotal role in the resulting immune responses. Prolyl cis/trans isomerization plays a fundamental role in the form of the secondary structure and the folding of proteins. This review covers some of the emerging evidence indicating the impact of prolyl isomerization on protein conformation, aberration of immune responses, and the development of hypersensitivity reactions.

Parity and Incidence of Thyroid Autoimmunity: A Population-Based Tehran Thyroid Study

Introduction: Autoimmune thyroid disease is the most common autoimmune disorder. Evidence regarding causes of the high prevalence and incidence of thyroid autoimmunity in women, and especially women of reproductive age, is still inconclusive and previous studies have suggested genetic, environmental, and existential factors to play a role in its pathogenesis. In this study, we aimed to investigate the effect of parity and other reproductive factors on the incidence of thyroid autoimmunity within the framework of the Tehran Thyroid Study (TTS). Materials and Methods: This study was conducted within the framework of the TTS and 1999 nonpregnant euthyroid thyroid peroxidase antibody (TPOAb) negative women were followed up for an average of 8.3 years. A pooled logistic regression model was used to assess the association (odds ratio) between time-dependent covariates parity, menopause, and abortion, and incidence of TPOAb positivity. Results: The total incidence rate of TPOAb positivity was 8.65 [7.35-10.18] per 1000 person-years. We found no significant association between changes in the number of parity and risk of developing TPOAb using multiple pooled logistic models both as crude effect and after adjustment for age, body mass index, and smoking. Similarly, there was no association between changes of parity, menopause, and abortion status, and incidence of TPOAb positivity. Conclusions: Parity does not seem to have an independent role in triggering thyroid autoimmunity, but vast immunological and physiological changes during pregnancy may act as a precipitating factor in the context of other genetic and environmental modifiers.

Do fetal extravillous trophoblasts circulate in maternal blood postpartum?

Introduction

Circulating fetal extravillous trophoblasts may offer a superior alternative to cell‐free fetal DNA for noninvasive prenatal testing. Cells of fetal origin are a pure source of fetal genome; hence, unlike the cell‐free noninvasive prenatal test, the fetal cell‐based noninvasive prenatal test is not expected to be affected by maternal DNA. However, circulating fetal cells from previous pregnancies may lead to confounding results.

Material and methods

To study whether fetal trophoblast cells persist in maternal circulation postpartum, blood samples were collected from 11 women who had given birth to a boy, with blood sampling at 1‐3 days (W0), 4‐5 weeks (W4‐5), around 8 weeks (W8) and around 12 weeks (W12) postpartum. The existence of fetal extravillous trophoblasts was verified either by X and Y chromosome fluorescence in situ hybridization analysis or by short tandem repeat analysis. To exclude technological bias in isolating fetal cells, blood samples were also collected from 10 pregnant women between a gestational age of 10 and 14 weeks, the optimal time frame for cell‐based noninvasive prenatal test sampling. All the samples were processed according to protocols established by ARCEDI Biotech for fetal extravillous trophoblast enrichment and isolation.

Results

Fetal extravillous trophoblasts were found in all the 10 samples from pregnant women between a gestational age of 10 and 14 weeks. However, only 4 of 11 blood samples taken from women at 1‐3 days postpartum rendered fetal extravillous trophoblasts, and only 2 of 11 samples rendered fetal extravillous trophoblasts at 4 weeks postpartum.

Conclusions

In this preliminary dataset on few pregnancies, none of the samples rendered any fetal cells at or after 8 weeks postpartum, showing that cell‐based noninvasive prenatal testing based on fetal extravillous trophoblasts is unlikely to be influenced by circulating cells from previous pregnancies.

Autoantibodies against islet cell antigens in children with type 1 diabetes mellitus

We investigated the prevalence of glutamic acid decarboxylase 65 autoantibody (GADA), insulinoma-associated protein 2 autoantibody (IA2A), and insulin autoantibody (IAA) in 750 children with type 1 diabetes (T1D) living in Taiwan. GADA, IA2A, and IAA were measured by radioimmunoassay. The data were assessed by χ² test, binary logistic regression, and Spearman rank correlation. Of the 750 T1D patients, 66.3% had GADA, 65.3% IA2A, 35.7% IAA, and 17.2% no autoantibodies. The prevalence of GADA and IA2A significantly decreased along T1D duration. The positivity of either GADA or IA2A was 89.4% within the first year of disease and decreased to 36.7% after 9 years (P = 1.22 × 10^–20). Female patients had significantly higher prevalence of GADA compared with male patients (72.3% vs. 59.7%, P = 0.00027). The patients diagnosed before 12 years of age had a positive rate of 92.2% for either GADA or IA2A. Patients diagnosed at age 12 or above had a significantly lower positive rate of 81.6% (P = 0.011). GADA and IA2A significantly correlated with each other (rs = 0.245, P = 1.09 × 10^–11). We concluded that autoantibodies were detectable in 89.4% of T1D patients within one year after diagnosis. Their prevalence declined with disease duration. GADA was more prevalent in female patients. GADA and IA2A weakly correlated with each other.

Recent advances in understanding autoimmune thyroid disease: the tallest tree in the forest of polyautoimmunity

Autoimmune thyroid disease (AITD) is often observed together with other autoimmune diseases. The coexistence of two or more autoimmune diseases in the same patient is referred to as polyautoimmunity, and AITD is the autoimmune disease most frequently involved. The occurrence of polyautoimmunity has led to the hypothesis that the affected patients suffer from a generalized dysregulation of their immune system. The present review summarizes recent discoveries unravelling the immunological mechanisms involved in autoimmunity, ranging from natural autoimmunity to disease-specific autoimmunity. Furthermore, the clinical grounds for considering AITD in a setting of polyautoimmunity are explored. A better understanding of these may pave the way for designing new treatment modalities targeting the underlying immune dysregulation when AITD appears in the context of polyautoimmunity.

Parity and Risk of Thyroid Autoimmunity Based on the NHANES (2001-2002, 2007-2008, 2009-2010, and 2011-2012)

CONTEXT

Autoimmune thyroid disease is more common in women than in men. Fetal microchimerism has been implicated as a potential explanation for this disparity.

OBJECTIVE

The objective of this study was to evaluate the relationship between parity and thyroid autoimmunity in the US population.

DESIGN, SETTING, PATIENTS

The National Health and Nutrition Examination Survey was used to identify females with antithyroperoxidase (TPOAb) and antithyroglobulin antibody (TgAb) measurements and parity data. Subjects (n = 4864) were categorized as never pregnant (n = 909) or previously pregnant (n = 3955). The association of parity with thyroid autoantibodies was examined both qualitatively and quantitatively. Thyroid autoimmunity was defined as TPOAb and/or TgAb titers above the reference limits.

RESULTS

Previous pregnancy carried an odds ratio (OR) of 1.55 [95% confidence interval (CI): 1.26 to 1.91] for thyroid autoimmunity compared with never pregnant. Number of pregnancies was associated with thyroid autoimmunity: OR = 1.37 (95% CI: 1.02 to 1.84); 1.4 (95% CI: 1.08 to 1.81); 1.52 (95% CI: 1.18 to 1.96); and 1.73 (95% CI: 1.38 to 2.18) for 1, 2, 3, and ≥4 pregnancies, respectively. Because ever-pregnant women differed in several variables-age, race, smoking status, history of thyroid disease, and urinary iodine level-from never-pregnant women (P < 0.001), a multivariate regression analysis was performed, which showed no association of pregnancy with thyroid autoimmunity. The association was further examined utilizing an age-matched analysis, which confirmed the absence of an association between thyroid autoimmunity and parity.

CONCLUSION

Although we initially observed a strong association between parity and thyroid autoimmunity, after controlling for age and other variables, we were unable to identify an association.