The role of T-lymphocyte subsets and interleukin-5 blood levels among Indian subjects with autoimmune thyroid disease

Abstract

Autoimmune Thyroid Disease (AITD) results from an interaction of exogenous and endogenous factors in a genetically predisposed individual. AITD is being increasingly reported among the Indian population. Lymphocyte subsets and levels of interleukin-5 (IL- 5) were studied in the peripheral blood of patients with AITD. Subjects diagnosed with either hyperthyroidism due to Graves' Disease (GD) or with primary hypothyroidism due to Hashimoto's Thyroiditis (HT) were consecutively recruited. Euthyroid controls were also recruited for comparison. Lymphocyte subsets (CD4 and CD8 counts, CD4/CD8 ratio) were evaluated by flow cytometry and IL-5 levels were determined by the sandwich ELISA method. Nineteen subjects with GD, 16 subjects with HT and 10 controls were studied. CD4/CD8 ratios were found to be significantly lower only in subjects with HT compared to controls. Serum IL-5 values were significantly higher in both GD and HT in comparison to controls. The study found increased levels of IL-5 and reduction in ratios of CD4/CD8 lymphocytes in the peripheral blood of patients with HT, but only IL-5 was increased in GD. High levels of IL-5 could have resulted in the high titres of antithyroid antibodies and may therefore be considered to play a more significant role than peripheral lymphocytes in the pathogenesis of AITD in the Indian population.