Immunoregulation by Progesterone: Effects on Immune Cells and Mesenchymal Stem Cells

Progesterone is a steroid hormone which basic biological role is to sustain the successful development of pregnancy. It is a major player in regulation of immune communications between mother and foetus. However, progesterone has shown to be a very potent immunomodulator influencing both the afferent and the efferent hand of the immune response. Numerous studies have demonstrated that progesterone modifies the activity of the T cell population. It's known that it suppresses the Th1 and favors the Th2 type cytokine secretions, inhibits the cytotoxicity of T cells and increases the differentiating of Th0 cells as T regs. Similarly, inhibitory effect is exerted by progesterone on the activities of NK cells. Also under the influence of progesterone the percentage of asymmetric antibodies is increased as the intimate mechanism is glycosilation of the Fab fragment of the IgG molecules which makes them rather blocking than efficient antibodies. Newly identified targets of progesterone are dendritic cells and mesenchymal stem cells. Progesterone alters the dendritic cells making them recruit predominantly cells with pro-tolerogenic activities. Furthermore, progesterone upregulates the immunomodulatory proteins secretion by mesenchymal stem cells.