Human Leptin Hormone Affects TNF-α Production in Mucosal-associated Invariant T Cells

Mucosal-associated invariant T (MAIT) cells are striking lymphocyte population in the blood and their importance in immune responses is growing fast. The current study was conducted to evaluate leptin hormone effects on MAIT cell functions.
Five healthy male donors in ages of 22-30 years were selected and peripheral blood mononuclear cells (PBMCs) were enriched by Ficoll-density gradient. The cells were stimulated by different doses of human recombinant leptin. Using anti-CD3, anti-CD161 and anti-Vα7. 2 antibodies, positive CD3/CD161/ Vα7.2 MAIT cells were selected among stimulated PBMCS and proliferation alterations (after 5 days) and intercellular tumor necrosis factor (TNF)-α production (after 24 hours) were determined by flow cytometer.
Stimulation of MAIT cells in doses of under 800 ng/ml of leptin did not alter the frequency of the cells significantly. However, in 800 ng/ml of leptin the number of the cells declined substantially, but statically analysis did show a significant difference with unstimulated and other leptin concentrations (p=0.12). When the frequency of intracellular TNF-α positive MAIT cells investigated, it revealed that in doses of 250 and 400 ng/ml of leptin, the number of the TNF-α. positive cells significantly increased compared to other concentrations (p=0.002). In high concentration of leptin (800 ng/ml), the frequency of positive TNF-α cell decreased compared to 400 ng/ml of the hormone.
Leptin hormone in doses of 250 and 400 ng/ml has affected MAIT cells’ ability to produce TNF-α cytokine. Therefore, in adipose tissue leptin might be considered as a new source of inflammatory cytokines.