The role of glycodelin in the conversion of Cd11b⁺ cells to MDSC and the regulation of their functional activity

Abstract

The amniotic variant of glycodelin (Gd) has pronounced immunomodulatory properties and is involved in the formation of immune tolerance during pregnancy. The role of recombinant Gd at physiological (0.2 and 2 μg/ml) and superphysiological (10 μg/ml) concentrations in regulating the differentiation and functional activity of human myeloid-derived suppressor cells (MDSCs) was investigated in vitro. MDSCs were generated from CD11b+ peripheral blood cells of healthy donors by two-step induction (IL-1β + GM-CSF and then lipopolysaccharide (LPS). The effect of Gd on the content of polymorphonuclear MDSC (PMN-MDSC) and monocytic MDSC (M-MDSC), intracellular expression of indoleamine 2.3-dioxygenase (IDO), arginase-1 (Arg1, and cytokine profile in cell cultures was investigated. In general, the transformation of CD11b+ cells into MDSCs exhibits the following characteristics: as a result of cytokine induction, predominantly M-MDSCs but no PMN-MDSCs are formed and Arg1 expression is virtually undetected. Gd was found to increase the number of M-MDSCs at concentrations of 2 and 10 μg/ml. Gd was found not to affect Arg1 expression but increased the percentage of MDSCs expressing IDO (10 μg/ml). Gd also modulated the cytokine profile of CD11b+ cells by suppressing the production of IL-19, IL-26 and TWEAK/TNFsF12 at a physiological concentration of 2 μg/ml and the production of IFN-α2 and IL-26 at a supraphysiological concentration. Thus, the role of Gd in the conversion of CD11b+ cells to MDSCs was examined under conditions of cytokine induction in vitro.