A simple method to identify bone marrow mesenchymal stromal cells with a high immunosuppressive potential

Background aims. The benefi cial activity of mesenchymal stromal cells (MSC) in allogeneic hematopietic stem cell transplantation requires correct use in terms of cell dose and timing of infusion and the identifi cation of biomarkers for selection. The immunosuppressive bone marrow (BM)-derived MSC (BM-MSC) functions have been associated with the production of soluble HLA-G molecules (sHLA-G) via interleukin (IL)-10. We have established a reliable method for evaluating BM-MSC HLA-G expression without the infl uence of peripheral blood mononuclear cells (PBMC). Methods. Thirteen BM-MSC from donors were activated with recombinant IL-10 or co-cultured with 10 different phytohemagglutinin (PHA)- treated PBMC (PHA-PBMC). Membrane-bound and sHLA-G expression was evaluated by fl ow cytometry and enzymelinked immunosorbent assay (ELISA), respectively; lymphoproliferation was measured by (methyl- 3H)thymidine. Results. The results demonstrated the ability of IL-10 to stimulate both membrane-bound and sHLA-G production by BM-MSC. The levels of HLA-G expression induced by IL-10 in BM-MSC were associated with the inhibition of PHA-PBMC proliferation (sHLA-G, P 0.0008, r 0.9308; membrane HLA-G, P 0.0005, r 0.9502). Conclusions. We propose the evaluation of sHLA-G production in IL-10-treated BM-MSC cultures as a possible marker of immunoregulatory function.