Inclusion Criteria:

- Status-post allogeneic stem cell transplant (includes cord blood transplant,
matched-unrelated-donor transplant and matched-related donor transplant) for any
indication.

- HLA matching needs to be 4-6/6 by at least intermediate resolution for class I + II
for cord blood and 5-6/6 for matched related or matched unrelated donors.

- Diagnosis of grade II-IV acute GVHD with histological confirmation of at least one
organ (skin, gut, or liver) within the last 14 days. Grading of acute GVHD is per the
standard Keystone criteria. Prior to enrollment, efforts should be made to rule out
diagnoses that may mimic GVHD, such as drug rashes or GI infection. Patients that are
being treated for acute GVHD and appear to be progressing to chronic GVHD are also
eligible

- No improvement, or worsening, of acute GVHD after at least 4 days of IV
methylprednisolone dosed at, at least 2.0mg/kg/day..

- Weight >25.0kg.

- Adequate venous access.

Exclusion Criteria:

- Evidence of veno-occlusive disease.

- Intubated patient.

- Patient receiving dialysis.

- Age > 30.

- Total bilirubin >15mg/dL