Study Comparing ABX-CBL (Monoclonal Antibody) Versus Atgam in Patients With Steroid Resistant Acute Graft Versus Host Disease

Inclusion Criteria: * Recipient of single allogeneic stem cell transplant from any donor type * Time post transplant less than 100 days * Received no treatment for GVHD other than steroids Exclusion Criteria: * Recipient of second allogeneic stem cell transplant or subsequent lymphocyte product from the donor post transplant * IBMTR index less than A * Received any murine product in the past * Diagnosed with chronic GVHD * Received Atgam later than day 10 post transplant * Change to prophylactic regimen for acute GVHD within 72 hours of randomization