|Year : 2018 | Volume
| Issue : 3 | Page : 128-131
Serum concentrations of interleukin-17A but not interleukin-17F are elevated in children with recent-onset Hashimoto's thyroiditis
Sandhya Cautha1, Devi Dayal1, Naresh Sachdeva2, Darshan Badal2, Savita Verma Attri1, Kushaljit Singh Sodhi3
1 Department of Pediatrics, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Endocrinology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
3 Department of Radiodiagnosis, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Web Publication||15-Nov-2018|
Dr. Devi Dayal
Department of Pediatrics, Pediatric Endocrinology and Diabetes Unit, Advanced Pediatrics Center, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012
Source of Support: None, Conflict of Interest: None
Background: Recent advances in immunology suggest that T-helper 17 lymphocytes (Th17) have a major role in the disrupted autoimmunity in Hashimoto's thyroiditis (HT). However, there are no data on the Th17 characteristics, especially regarding the dominant interleukins (ILs) that they produce in children with HT.
Material and Methods: With an aim to determine the role of two major Th17 cytokines in children with HT, we measured serum concentrations of IL-17A and IL-17F in 40 children with recent-onset HT and 40 age- and sex-matched controls by enzyme-linked immunosorbent assay.
Results: Serum IL-17A concentrations were significantly higher in children with HT when compared to controls (3.39 ± 6.93 pg/mL vs. 0.12 ± 0.47 pg/mL, P = 0.00). However, the IL-17F concentrations were similar in patients and the controls (11.12 ± 15.34 pg/mL vs. 9.68 ± 12.87 pg/mL, P = 0.65).
Conclusions: The elevated concentrations of IL-17A, one of the major effector cytokines of the Th17 system, suggest its possible role in the pathogenesis of HT in children.
Keywords: Children, cytokines, Hashimoto's thyroiditis, interleukin-17A, interleukin-17F, interleukins, T-helper 17 lymphocytes
|How to cite this article:|
Cautha S, Dayal D, Sachdeva N, Badal D, Attri SV, Sodhi KS. Serum concentrations of interleukin-17A but not interleukin-17F are elevated in children with recent-onset Hashimoto's thyroiditis. Thyroid Res Pract 2018;15:128-31
|How to cite this URL:|
Cautha S, Dayal D, Sachdeva N, Badal D, Attri SV, Sodhi KS. Serum concentrations of interleukin-17A but not interleukin-17F are elevated in children with recent-onset Hashimoto's thyroiditis. Thyroid Res Pract [serial online] 2018 [cited 2019 Mar 26];15:128-31. Available from: http://www.thetrp.net/text.asp?2018/15/3/128/245558
| Introduction|| |
Hashimoto's thyroiditis (HT), the most common autoimmune thyroid disease in children and the main cause of primary hypothyroidism in iodine-sufficient areas of the world, is a classical example of organ-specific autoimmunity., The disease is characterized by the progressive loss of follicular cells and replacement of the thyroid tissue by lymphoid infiltrates and fibrosis. The disruption of the thyroid architecture and the loss of functional tissue results in the development of progressive hypothyroidism. The disruption of the autoimmune response in HT, previously considered to be T-helper type 1 (Th1)-mediated, is now believed to be mainly driven by the Th17 lymphocytes. Increased proportions of Th17 cells both in the peripheral blood and thyroid gland of adult patients with HT have been found in recent studies., In addition, highly upregulated interleukin 17 (IL-17) mRNA expression in the serum and thyroid tissues indicates an important role of Th17 lymphocytes in the cell-mediated cytotoxicity. The conventional Th17 lymphocytes are specified with production and excretion of IL-17A-F, IL-21, and IL-22 which mainly intensify the release of other proinflammatory cytokines such as IL-β, tumor necrosis factor alpha, and chemokines. The production and excretion of a specific type of IL are believed to be a consequence of sustained exposure of the conventional Th17 lymphocytes to different cytokines. Due to high plasticity, Th17 lymphocytes may differentiate to perform different functions. The consistent observation of an increase in IL-23 in patients with HT is probably linked to the differentiation of Th17 to produce cytokines involved in the thyroid cellular damage. Under the prolonged influence of IL-23, the Th17 lymphocytes differentiate into specialized Th1-like (nonclassic Th1) pathogenic cells with the ability to synthesize interferon-γ and granulocyte-macrophage-colony-stimulating factor. Thus, the Th17 cell type influences the pathogenesis of molecular damages in HT. However, despite intense research on the characterization of Th17 lymphocytes by the type of cytokine production in recent years, there is scarce information on the exact type of Th17 lymphocytes that play a dominant role in the pathogenesis of HT. All the previous studies were done in adult patient populations of HT.,,, The available studies were either small or did not study patients with recent diagnosis of HT when the pathogenetic mechanisms are more likely to be elucidated., It is not known if the mechanism of Th17-mediated inflammation is similar in children and adults with HT. We thus aimed to characterize the Th17 responses by determining the serum concentrations of the two major circulating forms of Th17 cytokines in children with recent-onset HT.
| Materials and Methods|| |
Children with recent-onset HT (<3 months of diagnosis) aged 6–12 years who attended the pediatric endocrinology clinic of our tertiary care teaching hospital in North India from May 2016 to December 2017 were included in the study. The diagnosis of HT was based on the presence of symptoms suggestive of hypothyroidism along with the presence of any one of the following three parameters: positive anti-thyroid peroxidase (anti-TPO) antibodies, chronic lymphocytic infiltrate on histological examination, and diffuse hypoechogenicity on thyroid ultrasound. Those with acute infections and comorbidities related to HT, which may affect IL levels, were not included. Measurement of serum total triiodothyronine (T3), total thyroxine (T4), and thyroid-stimulating hormone (TSH) was done to determine thyroid functional status. Age- and sex-matched healthy controls were recruited as controls after taking history to exclude current and past thyroid illness as well as any autoimmune, inflammatory, or neoplastic disease. The controls were recruited from the general pediatric outpatient department and included children who came for minor noninfectious illnesses or routine vaccinations. An informed consent from parents or caregivers and assent from children was obtained before enrollment. The Institute Ethics Committee (Intramural) of PGIMER, Chandigarh approved the study protocol (INT/IEC/2017/1446).
Peripheral blood samples were drawn in plain vacutainers from patients and controls after an overnight fast for measurement of serum IL-17A and IL-17F concentrations. Samples were immediately centrifuged at 4500 g for 5 min at +4°C and stored at −80°C for subsequent cytokine analysis. All samples from patients were obtained before initiation of the levothyroxine therapy. Serum concentrations of total T3, T4, TSH, and anti-TPO antibodies were measured by electrochemiluminescence immunoassay on an Elecsys 2010 analyzer using specific kits (Roche Diagnostics, Germany). Serum levels of ILs were measured by enzyme-linked immunosorbent assay (ELISA) kits (Human IL-17A Platinum ELISA BMS2017 and Human IL-17F Platinum ELISA BMS2017, eBioscience, San Diego, CA, USA) on an ELISA reader (Tansasia Biomedicals Ltd) and the results were expressed as pg/mL. The minimum detection limit for IL-17A and IL-17F was 0.5 pg/mL and 4.0 pg/mL, respectively.
Statistical Software for Social Sciences (SPSS) (IBM SPSS Statistics for Windows, Version 22.0, IBM Corp, Armonk, NY, USA) was used for performing the statistical analysis. Comparison of serum concentrations of IL-17A and IL-17F between cases and controls was done using Mann–Whitney U test and among subgroups of cases by three-way ANOVA test. Post hoc analysis was performed using Tukey's range tests to identify differences between the subgroups. Correlation of IL-17A and IL-17F levels with age at diagnosis, Body Mass Index (BMI), and anti-TPO antibodies was done by Spearman's correlation coefficient. All tests were two-tailed, and value of P < 0.05 was considered statistically significant.
| Results|| |
The demographic characteristics of the study population are shown in [Table 1]. The mean serum concentrations of IL-17A were significantly higher among cases as compared to controls [Table 2]. However, the difference between IL-17F concentrations among cases and controls was not statistically significant [Table 2]. The subgroups of children with overt hypothyroidism, subclinical hypothyroidism, and euthyroid status had similar mean serum concentrations of IL-17A (5.7 ± 9.2, 2.0 ± 4.4, and 0.30 ± 0.6 pg/mL, respectively, P = 0.16) and IL-17F (13.0 ± 17.7, 7.4 ± 7.6, and 17.7 ± 25.4, respectively, P = 0.34).
|Table 1: Demographic characteristics of patients with recent-onset Hashimoto's thyroiditis and their healthy controls|
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|Table 2: Comparison of mean serum concentrations of interleukin-17A and interleukin-17F between cases and controls|
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There were no gender differences in the mean serum concentrations of IL-17A (4.3 ± 6.9 vs. 2.4 ± 6.9 pg/mL, P = 0.28) and IL-17F (12.1 ± 16.5 vs. 10.1 ± 14.4 pg/mL, P = 0.51). Spearman coefficient correlation showed no association of age at diagnosis, BMI and anti-TPO antibody levels with IL-17A (P = 0.84, 0.97, and 0.54, respectively) or IL-17F concentrations (P = 0.38, 0.39, and 0.29, respectively).
| Discussion|| |
Recent research indicates a dominant role of Th17 lymphocytes in the pathogenesis of HT. The characterization of the Th17 cell subtypes by the type and quantity of specific cytokine production is critical for understanding the complex molecular mechanisms of chronic inflammation in patients with HT and developing treatment tools by specific targeting. The results of our study show that the serum concentrations of IL-17A are much higher in children with HT as compared to controls indicating a major role of IL-17A secreting Th17 cells in the pathogenesis of HT in these children. The results are consistent with several recent studies in adults and in experimental animal models.,,,,,,
A lower occurrence of HT in IL-17−/− (knockout mice) as compared to control (IL-17+/+) mice suggested the pivotal role of Th17/IL-17 in the development of HT. Similar observations on the role of Th17 cells were made by several authors in subsequent studies on patients with HT. Figueroa-Vega et al. found significantly higher levels of IL-17+ and IL-22+ lymphocytes and IL-17 mRNA levels in peripheral blood and thyroid tissues of patients with HT as compared to patients with Graves' disease and healthy controls. Qin et al. also found higher mRNA levels of IL-17A and IFN-γ in both peripheral blood mononuclear cells and thyroid tissues of HT patients than in controls and concluded that similarly high levels of IL-17A and IFN-γ suggested a mixed response of Th17 and Th1 in HT where both cells may play important roles in the destruction process by cell-mediated cytotoxicity. In a recent study by Konca et al., the levels of IL-17 and IL-23 were expressed in higher concentrations in patients with HT in comparison to controls. Another recent study showed higher levels of IL-17A in patients with recent-onset HT as compared to age- and sex-matched healthy controls.
The exact molecular mechanisms of Th17/IL-17-mediated immune destruction of thyroid cells are unclear at present. Animal studies suggest that IL-17 exacerbates the cellular and biochemical events of the acute phase of inflammation. It thus plays an important role in sustaining the ongoing inflammation, unlike IL-23 which is involved in the induction of inflammation through the promotion of Th17 cell differentiation and other mechanisms in patients with HT., Li et al. showed significantly increased intra-thyroid infiltrating Th17 cells and serum IL-17 levels in patients with HT. The concentration of serum IL-17 was inversely correlated with patients' residual thyroid function while the heterogeneously expressed thyroid IL-17 directly correlated with local fibrosis indicating a direct role of IL-17 cytokines and Th17 cells in the destruction of thyroid tissue in HT.
We chose to include IL-17F estimation as it shares the strongest sequence homology with IL-17A and a possible shared pattern of expression owing to close location of the genes encoding these two cytokines. In addition, both these ILs are presumed to mediate pro-inflammatory responses. Despite these similarities, the role of IL-17F is poorly understood, and there are no previous studies on patients with HT. In the present study, the serum concentrations of IL-17F were not significantly elevated in patients indicating that this cytokine may have little role in HT. Our observations are similar to previous studies which suggested differential roles of IL-17A and IL-17F depending upon the type and site of inflammation. However, it has to be understood that IL-17F forms only a small fraction of the total circulating IL-17 in the blood and measurement of IL-17F mRNA levels in the peripheral blood or thyroid tissue would be more sensitive for ascertaining its role in the pathogenesis of HT.,
The results of our study indicate that the pathogenesis of Th17-mediated on-going inflammation in HT in children is probably similar to adults and is characterized by a predominant IL-17A secreting Th17 cell type previously demonstrated in adult populations with HT.,,,, Prospective enrolment of an equal number of boys and girls in our patient cohort hints at no female preponderance commonly reported in HT, similar to our previous data in HT. Further larger studies that include estimation of IL-17A mRNA levels in the peripheral blood, as well as thyroid tissues in children with HT, are suggested.
| Conclusions|| |
Children with recent-onset HT have higher serum concentrations of IL-17A as compared to matched healthy controls. Age, gender, and thyroid status did not affect the IL concentrations. A possible role of IL-17A cytokines, one of the major effector cytokines of the Th17 system, needs further exploration in larger studies in children with HT.
The funds for this research were provided by PGIMER, Chandigarh through the Special Research Grant for MD thesis (LP 480/2017).
Financial support and sponsorship
The funds for this research were provided by PGIMER, Chandigarh through the Special Research Grant for MD thesis (LP 480/2017).
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]