The effect of rabbit antithymocyte globulin on human mesenchymal stem cells

Summary Mesenchymal stem cells ( MSC s) possess immunomodulatory properties which are of key interest for their application in autoimmunity and transplantation. In transplantation, administration of MSC s has shown promising results in preclinical models and has recently moved to clinical trials. Therefore, it is important to study the interactions between MSC s and immunosuppressive drugs currently used in transplantation. We aimed to analyze the effect of rabbit antithymocyte globulin ( rATG ) MSC s. MSC s were obtained from perirenal fat of kidney donors and exposed to ranging doses of rATG (Thymoglobulin ® , Genzyme; 0.5–100 μg/ml). Binding of rATG , effects on viability and susceptibility to be killed by cytotoxic lymphocytes as well as effects on their immunosuppressive potential of MSC s were tested. rATG binds dose‐dependently to MSC s. This binding was associated with slightly impaired viability after 48 and 72 h when compared with nonexposed MSC s. In contrast to nontreated MSC s, rATG preexposed MSC s were susceptible to be lysed by cytokine‐activated CD8 + cytotoxic cells and NKT cells. The capacity of MSC s to suppress the proliferation of anti‐CD3/CD28 activated CD4 and CD8 T cells were reduced by the presence of rATG in the culture. rATG reduces the viability and antiproliferative capacity of MSC s in a dose‐dependent manner and converts them into targets for CD8 T cells and NKT cell lysis.