There will be a minimum of 62 study visits spread out over 4 years after transplant. Vital signs measurement, adverse event and OI reporting, medication history, physical exam, and blood collection will occur at selected visits. Sirolimus withdrawal will begin when a participant meets certain study criteria. The withdrawal process will occur over a minimum of 3 months at an approximate rate of 33% of the pre-withdrawal dose per month. Participants eligible for sirolimus withdrawal will undergo several kidney biopsies, including one 2 weeks prior to the start of withdrawal, 6 and 12 months after completion of withdrawal, 1 year after study enrollment, and annually thereafter.