Activated Naive CD4 + Peripheral Blood T Cells in Autoimmune Thyroid Disease

To better understand the clinical significance of changes in lymphocytes in thyroid disease this study analyzed the proportion of CD19⁺, CD3⁺, CD4⁺, and CD8⁺ cells among circulating lymphocytes in Graves' disease (GD, n = 34) and autoimmune hypothyroidism (AH, n = 28) vs healthy subjects (n = 15). In addition, the expression of CD25 and CD45 isoforms on CD4⁺ T cells as well as their modulation by methimazole in patients with GD was measured using three color flow cytometry. It was observed that, irrespective of age, both patients with GD (17.6 ± 7.0% ± SD) and those with AH (19.0 ±9.5%) had an increased percentage of the CD25⁺CD45RA⁺ (naive) subpopulation of helper cells vs healthy subjects (7.9 ± 2.3%, p < 0.0001). In patients with AH peripheral memory cells and hence overall CD25⁺ cells were more frequent among helper cells (56.7 ± 12.2%) than in healthy subjects (40.8 ± 14.0%, p < 0.001). Patients with GD (46.2 ± 13.4%) did not differ from normal subjects in this respect. Treatment of GD with MMI reduced the percentage of CD25⁺CD45RA⁺ cells among CD4⁺ cells toward values seen in healthy subjects. In addition, we confirm previous reports that CD8⁺ cells are significantly reduced in AH (23.9 ±4.9%) and untreated Graves' disease (23.2 ± 6.6%) vs healthy subjects (32.2 ± 5.9%,p < 0.001). We conclude that (i) subjects with autoimmune thyroid disease harbour an increased proportion of activated (CD25⁺) CD45RA positive helper T cells and exhibit a reduced percentage of CD8 cells; and (ii) action of MMI on peripheral naive CD25⁺ helper cells as well as on the percentage of CD8 cells in GD may in part relate to its thyrostatic effect and reflect immunomodulatory action.