Uptake and delivery of antigens by mesenchymal stromal cells

Background aimsMesenchymal stromal cells (MSCs) are multipotent stem cells with immunosuppressive properties. Nevertheless, it has been previously reported that MSCs might also trigger the immune response. We studied whether MSCs may act as carriers, capturing antigens that can be endocytosed by antigen-presenting cells later on.MethodsWe measured the cellular uptake of mannose receptor-mediated fluid phase macropinocytosis, assessed as cellular uptake of fluorescein isothiocyanate-dextran, and PKH-67-labeled cell lysates as a surrogate marker for antigen capture among dendritic cells (DCs, positive control), T lymphocytes (negative control) and MSCs.ResultsAll experiments confirmed that MCSs displayed pinocytic and endocytic capacities, which were lower than those observed for DCs but significantly higher than those observed for T cells. We also demonstrated that MSCs release previously endocytosed antigens, which subsequently can be captured by DCs.ConclusionsMSCs have the ability to capture and release antigens.