A Multicenter, Prospective Blood Collection Study in a Kidney Transplant Population

Inclusion Criteria: 1. Willing and able to provide written informed consent 2. Is 18 years of age or older at enrollment 3. Had a kidney transplant prior to enrollment 4. Is having an indication (for cause) biopsy as determined by clinician 5. retrospective leftover samples are available from the kidney donor(s). Exclusion Criteria: 1. Is pregnant 2. Had a blood transfusion within the past 4 weeks 3. Had a transplant from an identical (monozygotic) twin 4. Had transplants of multiple organs from the same donor (eg, kidney and liver transplant). 5. Had transplants of more than 2 organs from different donors (eg, recipient of a third kidney transplant) 6. Had a transplant of hematopoietic stem cells (eg, bone marrow) or tissue (eg, heart valve)