engleski

T-cell activation and age-related effects influence quantitative characteristics of Hashimoto's thyroiditis phenotype

Hashimoto's thyroiditis (HT) is the most frequent autoimmune thyroid disorder mediated by deregulated T-cell responses. Several gene candidates with immune regulatory functions have been implicated in HT etiology, including vitamin D receptor(VDR), cytotoxic T-lymphocyte antigen-4 (CTLA-4), CD28 and CD45 genes. Aim: To evaluate clinical implications of VDR, CTLA-4, CD28 and CD45 mRNA expression profiles in peripheral T- cells of HT patients. Materials and methods: 42 HT patients (mean age 46±14.8 years, 3 male) were diagnosed on the basis of positive thyroid peroxidase autoantibodies (TPOAb), characteristic echosonographic findings, cytopathological features consistent with HT in high quality, ultrasound-guided fine needle aspiration biopsies and/or biochemical hypothyroidism (median TSH 5.27 mU/L, interquartile range 3.11-13.8 mU/L). Pretreatment TPOAb-IgG (median TPOAb titer 285 IU/mL, interquartile range 77-1777 IU/mL) were measured by an enzyme-linked immunoassay calibrated against WHO reference MRC 66/387. At baseline, thyroid gland volume was measured by ultrasonography. Untouched T-lymphocytes were negatively isolated from peripheral blood of HT patients using magnetic beads procedure. Following T-cell isolation, total RNA was extracted and gene expression studied by RT-PCR. ImageQuantTL program was used for relative quantification of RT-PCR bands. An internal control gene was GAPDH. Comparative analysis of gene expression data versus FT4, FT3, TSH, TPOAb levels and goitre volume measurements was performed by Spearman rank correlations. Results: VDR, CTLA-4, CD28 and five isoforms of CD45 mRNA (CD45RABC, CD45RAB, CD45RBC, CD45RB andCD45R0) were expressed in most of the HT patients (n=36). Statistically significant positive correlation was detected between expression of the CD45RAB isoform and FT3 serum levels at diagnosis (P=0.0066, Spearman’s rho=0.51).Furthermore, CD45R0 isoform expression in peripheral T-lymphocytes was positively associated with age (P=0.027, rho=0.34). Conversely, a negative correlation was detected between CD45RABC mRNA expression and goiter volume (P=0.032, rho=-0.364). However, no significant association was found between total levels of VDR, CTLA-4 or CD28 mRNA expression and quantitative characteristics of HT phenotype. Conclusion: Unlike naive T-cells which preferentially express large CD45 isoforms (CD45RABC, CD45RAB and CD45RBC), activated and memory Tlymphocytes express the shortest one, CD45R0, which lacks RA, RB and RC exons, respectively. Our results indirectly suggest that peripheral FT3 levels and HT disease severity are significantly influenced by differentiation process and activation status of T-cells. Furthermore, higher prevalence of T- cells expressing CD45R0 activation marker in older HT patients emphasizes influence of age on T-cell development and function.

CD45 ; isoform ; CD28 ; receptor ; calcitriol ; CTLA-4 ; gene ; expression ; Hashimoto's thyroiditis ; T-cells

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