Only patients with Ann Arbor score 3 GVHD, will be eligible for this study treatment. It is important to understand that Ann Arbor GVHD grading is not approved for clinical use. It can only be used as a test for research purposes. In this study, patients must have their blood tested to determine, if they qualify as Ann Arbor score 3 GVHD, and must start the study treatment within 3 days of starting systemic steroid treatment for acute GVHD.