Leptin regulates thymic plasmacytoid dendritic cell ability to influence the thymocyte distribution in vitro

Leptin, the adipocyte-derived hormone, involved in regulating food intake and body weight, plays an important role in immunity and reproduction. Leptin signals via the specific membrane receptors expressed in most types of immune cells including dendritic cells (DCs) and thymocytes. Leptin enhances thymopoiesis and modulates T-cell-mediated immunity. Thymic plasmacytoid DCs (pDCs) are predominated in the thymus. They play an important role in thymocyte differentiation. We have analyzed whether leptin mediates its effects on human thymocytes by influencing on pDCs. We used leptin at concentration corresponding to its level during II-III trimesters of physiological pregnancy. We cultivated leptin-primed pDCs with autologous thymocytes and estimated the main thymocyte subsets expressing αβ chains of the T-cell receptor (αβTCR), natural regulatory T-cells (tTreg), natural T-helpers producing interleukin-17 (nTh17) and invariant natural killer T-cells (iNKT) in vitro. We have shown that leptin augmented CD86, CD276 expressions and depressed IL-10 productions by pDCs. Leptin-primed pDCs decreased the percentage of CD4⁺CD8⁺αβTCR⁺ thymocytes, increased CD4^hiCD8^-/loαβTCR⁺ cells. pDCs cultivated with leptin decreased the number of iNKT precursors, and did not change the number of tTreg and nTh17 precursors. Thus, leptin's important role in regulation of thymic pDC abilities to influence on the thymocyte distribution was indicated in vitro.