Treatment options for steroid-refractory GVHD (SR-GVHD) are unsatisfactory and prognosis is poor. The use of conventional intensive therapies to inhibit T-cells and inflammatory cytokines often result in high response rates ranging between 30 and 70%, but consistently long-term survival is limited ranging between 5 and 30% [12, 13] . Available therapies are limited both by lack of response as well as by high mortality from infectious complications related to intensive immunosuppression. There is immediate need to develop effective and safe therapies for SR-GVHD.