The purpose of this multi-center (observational) registry study is to establish a database of clinical and laboratory information that may help to identify any unique characteristics of tolerant participants that differ from participants who reject their kidney after discontinuing immunosuppressive drugs.

Following kidney (renal) transplantation, one possible complication is rejection of the new kidney. This occurs as a results of the body's immune system attacking (or rejecting) the newly transplanted kidney. After transplant, medicines known as "immunosuppressive" or "anti-rejection" drugs are given to transplant recipients to help prevent rejection of the transplanted kidney. If a transplant recipient stops taking these medicines, they almost always reject their transplanted kidney. However, in some exceptionally rare instances, transplant recipients who stop taking these drugs do not reject their kidney, and the kidney keeps working. The recipients are said at that point to "tolerate" the transplanted kidney, and this condition is referred to as "tolerance".

In this study, participants will be asked to provide consent for the collection of extensive demographic and clinical information; medical histories; and blood and urine samples. Blood and urine samples collected will be used to perform specific assays to help define mechanisms of tolerance.

Originally the study included 11 groups as listed; however, at present only groups 1,4, and 8 remain active. Whereas the initial study duration was 6 years, this was extended to 11 years in order to follow over more extended time a B cell signature identified for tolerant kidney subjects and how this signature may change. (Refer to publications section: Newell, Kirk et al, J Clin Invest. 2010).

Inclusion Criteria:

• Must be a renal transplant recipient or living donor
• Meet the criteria for inclusion in one of the study enrollment groups
• Provide informed consent

Exclusion Criteria:

• AIDS [includes all HIV-infected persons who have less than 200 cells/mm(3) CD4+ T-lymphocytes/microL, or a CD4+ T-lymphocyte/micro liter or a CD4+ T-lymphocyte percent of total lymphocytes less than 14, or who have been diagnosed with an AIDS-defining condition as defined by the Centers for Disease Control and Prevention (CDC)
• Current malignancy requiring recent surgery, ongoing chemotherapy or radiation
• Acute systemic infections within 30 days prior to enrollment
• Pregnancy
• Transplant of another organ

Note: Patients meeting any of the exclusion criteria, if identified to have been clinically tolerant prior to the occurrence of the excluding condition, will be enrolled and demographic data collected for the registry; however, the decision as to whether or not to collect blood, urine, and tissue samples will be deferred until the participant's condition improves and the clinically tolerant state persists.](streamdown:incomplete-link)

• Primary Care Clinics
• Major Kidney (Renal) Transplant Programs

Participant level data access is available to the public in: 1.) the Immunology Database and Analysis Portal (ImmPort), a long-term archive of clinical and mechanistic data from DAIT-funded grants and contracts; and 2.) TrialShare, the Immune Tolerance Network (ITN) Clinical Trials Research Portal.