###### Abstract  
Mesenchymal stem cells (MSCs) represent a population of adherent cells that can be isolated from multiple adult tissues. MSCs have immunomodulatory capacity and the ability to differentiate into many cell lines. Research study examines the immunomodulatory properties of MSCs isolated from chorion (CMSCs). Following the stimulation process, it was found that MSCs are capable of immunomodulatory action via the release of bioactive molecules as well as through direct contact with the immune cells. Immunomodulatory potential of the CMSCs was analyzed by modifying proliferative capacity of mitogen-activated lymphocytes. CMSCs and lymphocytes were tested in cell-to-cell contact. Lymphocytes were stained with carboxyfluorescein diacetate succinimidyl ester. Inhibition of the proliferation of activated lymphocytes was observed. Following the co-cultivation, the expression of markers involved in the immune response modulation was assessed. Afterwards, an increase in CMSCs expression of IL-10 was detected. Following the co-cultivation with activated lymphocyte, adhesion molecules CD54 and CD44 in the CMSCs increased. An increase of CD54 expression was observed. The properties of CMSCs, adherence and differentiation ability, were confirmed. The phenotype of CMSCs CD105+, CD90+, CD73+, CD44+, CD29+, CD45-, CD34-, CD54+ was characterized. It was demonstrated that chorion-derived MSCs have important immunomodulatory effects. choric mesenchymal stem cells; immunomodulation; lymphocytes +
Footnote †: journal: Applied  
CD71+, CD97+, CD98+, CD99+, CD106+, CD146+, CD155+, Stro-1+, CD166+, CD166+, CD271+, CD276+ and CD304+. These cells are characterized by the absence of hematopoietic markers, such as CD34-, CD79-, CD19- and major histocompatibility complex (MHC) class II molecules [10; 11]. Mesenchymal stem cells are involved in multiple interactions in the body. They act as immunomododulatory, antifibrosis and angiogenesis [12]. These cells also have the ability to create an immunomododulatory microenvironment and thus they help to minimize organ damage caused by inflammation and cells activated by the immune system [13]. The characteristic feature of stem cells is their ability to self-revise and differentiate into several types of tissues, predominantly mesenchymal as well as endo- and ectodermal tissues types. Numerous studies have described their differentiation into osteoblasts, chondrocytes, adipocytes, myocytes, epithelial cells and cardiomyocytes. Likewise, MSCs are capable of differentiating into neuroectodermal cells: neurons, astrocytes, oligodendrocytes and endodermal cells: hepatocytes [14; 15; 16; 17; 18; 19]. The immunomodulatory properties of MSCs are directly modulated by the environment where they are located. MSCs are modulated by various paracrine factors occurring in the inflammatory environment. The inflammatory environment also affects the cells of the adaptive immune system, especially T lymphocytes. MSCs were found to interact closely with immune cells, such as lymphocytes [20]. MSCs activated in this environment produce the paracrine-acting factors that act on cells of the immune system [21]. MSCs are also characterized by their mobility, and their ability to migrate to a higher incidence of inflammatory cytokines [22]. Following adequate stimulation, they are able to act by multifactor, direct contact and secretion of bioactive molecules, transforming growth factor \(\beta\)1 (TGF-\(\beta\)1), indoleamine 2,3-dioxygenase (IDO), hepatocyte growth factor (HGF), prostaglandin E2 (PGE2) and interleukin (IL-10) [23]. There are several causes of inflammation throughout the process, such as human leukocyte antigen ABC(HLA-ABC), CD90, activated leukocyte adhesion molecule CD166 (ALCAM) and other integrins that allow interactions of MSCs and T lymphocytes. Repeatedly, the inhibition of the proliferation of activated lymphocytes was observed during the co-cultivation of MSCs and mitogen-induced T lymphocytes [24].