A Cohort Study of Operationally Tolerant Allograft Recipients

Inclusion Criteria:

- Recipient of single organ liver or kidney allograft from a living or deceased donor;

- At screening, operationally tolerant, as defined by:

- Absence of any immunosuppressive therapy for >= 52 weeks prior to the screening
visit

- No evidence of allograft rejection in the 52 weeks prior to the screening visit,
based on the allograft recipient's medical history.

- Normal allograft function, defined respectively as:

1. liver function tests (ALT, GGT) for liver transplant recipients,

2. serum creatinine for kidney transplant recipients,

- below the upper limit of normal (ULN) as defined by ranges from Harrison's
Principles of Internal Medicine, 18th edition.

- Receiving regular follow-up for a kidney or liver transplant by a local physician.

--Participants must be willing to allow the study team to contact and share medical
information with this local physician.

- and ability to sign informed consent.

Exclusion Criteria:

- Current malignancy requiring recent surgery, ongoing chemotherapy, or radiation;

- Transplant of another organ;

- Current drug or alcohol dependency;

- Any medical condition that in the opinion of the principal investigator would
interfere with safe completion of the trial; and

- Inability to comply with the study visit schedule and required assessments.