Has a history of having undergone allogeneic stem cell transplantation, or any other allogeneic or xenogeneic transplant Subjects with a prior history of stem cell transplant (autologous and/or allogeneic) are allowed if History of allogeneic stem cell transplant. History of allogeneic stem cell transplant History of stem cell transplant. History of autologous or allogeneic stem cell transplant History of allogeneic organ or stem cell transplant Patients with a history of allogeneic stem cell transplant for MDS or any other antecedent hematologic disorder are not eligible History of autologous or allogeneic stem cell transplant History of (or plans to undergo) spleen removal surgery or allogeneic stem cell transplant History of allogeneic stem cell transplant Participants with a history of allogeneic stem cell transplant are eligible for study participation provided the following eligibility criteria are met: History of allogeneic stem cell transplant History of allogeneic stem cell transplant or transplant eligible History of an allogeneic stem cell transplant. Subjects with a history of an autologous stem cell transplant are NOT excluded if they meet inclusion criteria related to history of autologous stem cell transplant.