Inclusion Criteria:

- Patients must have a documented clinical diagnosis of grade II-IV acute graft-versus-
host disease defined as GVHD occurring within the first 100 days of transplantation

- Patients must be steroid-refractory defines as progression after 3 days of
corticosteroid therapy or no response after 5 days of corticosteroid therapy.

- Progression is defined as up-grading

- No response is defined as no down-grading

- Progression after 3 days requires patients to have received at least 2 mg/mg/day for
a total of 6 mg/kg of methylprednisolone or its equivalent.

- No response after 5 days requires patient to have received at least 2 mg/kg/d for a
total of 10 mg/kg of methylprednisolone or its equivalent.

- Patients with exacerbation of GVHD during steroid taper will require re-treatment
with 2mg/kg/d of corticosteroids and will need to meet the criteria

- Age 18-70

- Patients must have received an allogeneic hematopoietic stem cell transplant within
100 days of study enrollment.

- Serum creatinine < 2 mg/dL

Exclusion Criteria:

- Patients cannot have active CNS disease.

- Patients must not have received cyclophosphamide for GVHD prophylaxis

- Patients must not have pneumonia requiring oxygen supplementation

- Unable or unwilling to sign informed consent.