Abstract

Hypothyroidism and hyperthyroidism affect 5.9% of Americans over the age of 12. It is not known how dysregulation of thyroid hormones such as triiodothyronine (T3), impacts the immune system.

A laboratory model system was used to study the interactions between T3 and T cells. Jurkat T cells, a leukemic lymphocyte cell line, were cultured in fetal bovine serum (FBS) restricted growth media containing four different levels of T3. In order to assess T3 activity on proliferation and survival of Jurkat T cells, cell staining and flow cytometry-based techniques were used. Adding 10 µg/mL of T3 to culture media increased cell survival rates over a 20 day period (p<0.05) and allowed the cells to utilise palmitic acid (PA) as an alternative energy source. Adding T3 10 µg/mL significantly increased T cell proliferation over 12 days. While T3 was essential to T cell survival, it did not significantly affect T cell apoptosis and necrosis rates over 12 days. When 2 µM of PA and 10 µg/mL of T3 were added to the cultured cells, T cells survived better than with PA alone (p<0.05).

The data collected demonstrates that T3 promotes both the survival and proliferation rate of T cells cultured in 1% FBS media due to enhanced use of free fatty acids as fuel. This work has implications for how hypothyroidism and hyperthyroidism, impacts the proper functioning of the immune system. Low T3 levels could decrease T cell survival and proliferation, while high T3 levels may result in changes in T cell substrate utilisation.