A Cohort Study of Operationally Tolerant Allograft Recipients

Antirejection medicines, also known as immunosuppressive drugs, are prescribed to organ transplant recipients to prevent their bodies from rejecting the new organ. Some organ transplant recipients can stop taking anti-rejection medicines without rejecting their transplanted organ (this is called 'tolerance'). The purpose of this study will collect samples and data from 'tolerant' liver or kidney transplant recipients in order to find out: The purpose of this study is to collect samples and data in order to find out: * How long liver or kidney transplant recipients can remain tolerant; * What happens in the tolerant recipient's body over time; and * If there are patterns in the body that are linked to tolerance.

This is a multi-center, prospective, observational study in which operationally tolerant recipients of liver or kidney allografts will be followed longitudinally, with annual collections of clinical data and biological samples. All participants will be followed for the duration of the study, regardless of changes in their tolerance status. Participants will be recruited by three main pathways: 1. Tolerant participants from current and past Immune Tolerance Network (ITN) trials, including those who have already completed trial participation and those who are anticipated to complete trial participation, 2. Tolerant participants referred by ITN affiliated investigators, academic and community transplant physicians and directly through outreach to transplant affinity groups such as the National Kidney Foundation (NKF), and 3. Tolerant participants from the general transplant community who are reachable through general contact channels such as the ITN website, word-of-mouth referrals from existing participants, and social media.