Mesenchymal Stromal Cells Suppress T-and B-Cells via Galectin-9 in a Donor Dependent Manner

• Published in: Blood 2012-11, Vol.120 (21), p.1248-1248
• Main Authors: Ungerer, Christopher, Quade-Lyssy, Patricia, Henschler, Reinhard, Seifried, Erhard, Radeke, Heinfried, Schuettrumpf, Joerg
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V120.21.1248.1248

Abstract 1248 Therapeutic approaches using multipotent mesenchymal stromal cells (MSCs) are advancing in regenerative medicine, transplantation and autoimmune diseases. Until now the way of action for MSC-mediated immune suppression is still controversial and relies most probably on a multifactorial mechanism. MSCs have been demonstrated to produce the suppressive molecules hepatocyte growth factor (HGF), tumor growth factor-β (TGF-β), prostaglandin E2 (PGE2) and indoleamine 2,3-dioxygenase (IDO). Furthermore, it has been described that immunosuppression by MSCs is enhanced via stimulation with interferon-γ (IFN-γ). Recently, galectin-1, a β-galactoside binding lectin with immune modulatory properties, has been added to the group of immune modulatory molecules that are responsible for MSC-mediated immune suppression. Here, we identified galectin-9 (Gal-9) as a new molecule involved in MSC-mediated immune modulation. First, we isolated MSCs from bone marrow of randomly selected donors and performed several in vitro experiments regarding their immune modulatory potential (e.g proliferation and IgG production). Interestingly, Gal-9 was the only investigated protein, which was strongly upregulated in MSCs upon activation with IFN-γ. We moreover demonstrate that Gal-9 is a major mediator of the anti-proliferative effect of MSCs on T-cells. Although a B-cell suppressive function of Gal-9 has previously not been reported, we were surprised to detect the same inhibitory effect on isolated B-cells. Proliferation of immune cells was triggered upon either stimulation with either PHA and LPS, or CD40L and PHA. Activation of MSCs with IFN-γ resulted in a major decrease of proliferation of both T-cells and B-cells. In addition, Gal-9 and activated MSCs contribute to the suppression of VZV triggered immunoglobulin release as well. Again activation of MSCs with IFN-γ decreased the IgG release, whereas blocking Gal-9 with lactose, a well characterized inhibitor of Gal-9 function, reversed the effect almost completely. Further, we determined that Gal-9 expression levels (mRNA and protein) distinguish between MSC cultures from different donors after activation. Among donors, we could differentiate between individuals with high Gal-9 levels and higher immune modulatory potential and such with low Gal-9 expression and lower immune modulatory potential. Compared to untreated MSCs we demonstrated a three- to fifty-fold rise in Gal-9 levels after prior activation with IFN-γ. In a