Lower CD28+ T cell proportions were associated with CMV-seropositivity in patients with Hashimoto's thyroiditis

Abstract

Background: Alterations in the naive T cell subpopulations have been demonstrated in patients with T cell mediated autoimmune disorders, reminiscent of immunological changes found in the elderly during immunosenescence, including the switch from CD45RA + to CD45RO + T cells and decreased thymic function with increased compensatory proliferative mechanisms, partly associated with latent Cytomegalovirus (CMV) infection. The present study was aimed to investigate proportions of lymphocytes, their relation to CMV-seropositivity and the replicative history of CD45RA + expressing T cells in Hashimoto's thyroiditis (HT, n = 18) and healthy controls (HC, n = 70).

Methods: Proportions of peripheral T cells were investigated by flow cytometry. The replicative history was assessed by T cell receptor excision circles (TRECs) and relative telomere length (RTL). Expression of CD62L was analyzed by immunohistochemistry in thyroid sections. The role of CMV was assessed by serology, ELISPOT assay and in situ hybridization.

Results: Our results demonstrated a significant increase of CD28-negative T cells, associated with CMV-seropositivity in HT patients. HT showed abundant CD45RO + T cells with peripheral loss of CD62L-expressing CD8 + CD45RA + T cells, the latter mainly depending on disease duration. CD62L was expressed in thyroid lymphocyte infiltrations. The diagnosis of HT and within the HT group CMV-seropositivity were the main determinants for the loss of CD28 expression. RTL was not different between HC and HT. HT showed significantly lower TRECs in CD4 + CD45RA + T cells compared to HC.

Conclusions: Patients with HT display a peripheral T cell phenotype reminiscent of findings in elderly persons or other autoimmune disorders. Whether these mechanisms are primary or secondary to the immunological alterations of autoimmune conditions should be investigated in longitudinal studies which may open research on new therapeutic regimes for treatment of HT and associated autoimmune diseases.

Figure 1

Percentages of CD28-negative (A), CD45RO + (B) and CD45RA + CD62L + (C) CD8+ T cells patients with Hashimoto’s Thyroiditis (HT) and healthy controls (HC). Newly diagnosed HT patients are indicated as full circles. Hypothyroid patients are indicated by arrows. Horizontal lines indicate the median. Differences between HT and HC: ** p < 0.02, *** p < 0.01.

Figure 2

Percentages of CD28-negative CD8+ T cells in CMV-seropositive (CMV+) or CMV-seronegative (CMV-) patients with Hashimoto’s Thyroiditis (HT) and healthy controls (HC). Newly diagnosed HT patients are indicated as full circles. Hypothyroid patients are indicated by arrows. Horizontal lines indicate the median. Differences between HT and HC: *** p < 0.05, ** p < 0.02, *** p < 0.01.

Figure 3

Interferon-gamma-producing spot-forming-units (SFU) per 10⁶ cells in patients with Hashimoto’s Thyroiditis (HT) and healthy controls (HC). Peripheral blood mononuclear cells (PBMCs) were either stimulated with PHA (A) or with CMV pp65 antigen (B). A representative example of ELISPOT analysis showed similar results for HT patients and HC (C). Negative controls were unstimulated. Experiments were performed in duplicates.

Figure 4

CMV in situ hybridization in thyroid sections of Hashimoto‘s thyroiditis (HT) patients. Characteristic infiltrate in a patient with HT with oxyphilic follicular epithelium and surrounding lymphocytes without evidence of CMV DNA (A) compared to a positive control of CMV-induced colitis (B). Examples of CMV positive cells are indicated by arrows.

Figure 5

CD62L-expression in thyroid sections of Hashimoto‘s thyroiditis (HT) patients. Representative example of CD62L + mononuclear cell infiltrate in the thyroid gland of a patient with HT (A) compared to the thyroid gland of a healthy control (B) (20× magnification). Representative example of CD62L-expression within a characteristic lymphoid follicle in the thyroid gland of a patient with HT (10× magnification) (C). 40× magnification (D). Arrows indicate examples of CD62L + mononuclear cells.