This clinical trial is for men and women who have Epstein-Barr Virus- Associated Post-Transplant Lymphoproliferative Disorder (EBV-PTLD) following a solid organ transplant or Allogeneic Hematopoietic Cell Transplant (HCT) who did not respond well to treatment with rituximab or rituximab and chemotherapy.
   
The purpose of this study is to test how well tabelecleucel works for these groups of patients and to see what side effects may occur. 

Tabelecleucel is made by taking donor cells from a healthy person, growing the cells that fight EBV in a laboratory for several weeks, and then storing them in a freezer until they are matched to a patient in need of treatment.
  
Treatment with tabelecleucel is experimental which means it is not yet approved by the United States Food and Drug Administration (FDA).

All study participants will receive tabelecleucel via an intravenous infusion (IV). Participation in this study will last for approximately 5 years.