Mesenchymal stem cells (MSCs) are known as non-homogenous population of multipotent cells, which can expanded in vitro from the plastic-adherent cell population. Because of easy purification and differentiation potential, MSC are the first candidates of stem cells in clinical cell therapy. Recently, the immunomodulatory properties of MSCs has been studied for application in inflammatory responses, auto-immune disorders and organ transplantation. MSCs can regulate the immune response in many diseases. Studies have shown that adult MSCs can affect the immune cell responses. They can alter the cytokine secretion of dendritic cells by stimulating the secretion of regulatory cytokines such as IL-10 and inhibiting proinflammatory cytokines such as interferon (IFN)-γ. Neutrophils are one of the first defense lines against any invasion. The close interaction between MSC and neutrophils in the bone marrow niche improve the neutrophils survival thus enhance the immune function. Therefore it is critical that their turnover should be controlled. The immunoregulatory activities of MSCs are mediated by either cell-cell contacts or soluble factors. Previous evidence and our primary studies show that neutrophils are rescued from apoptosis upon incubation with MSCs or their supernatants. Incubation of MSC supernatant reduced the rate of apoptosis in Lipopolysaccharide (LPS)-stimulated neutrophils by secretion of interleukin 8/MIF (macrophage inhibitory factor). MSCs also decreased the pro-apoptotic protein (Bax) and increased mitochondrial antiapoptotic protein (MCL-1) via IL-6 signaling. Moreover, bone marrow-derived MSCs inhibit apoptosis of resting and IL-8 activated neutrophils in normal serum supplemented culture. Evidence reveal that the Immunomodulatory of MSCs, especially on neutrophils, can be considered for using them in clinical applications

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