This is a single-center, prospective, open label study in islet transplant recipients following islet graft loss.

After complete islet graft loss is determined, patient's maintenance immunosuppression (i.e. sirolimus, tacrolimus, MMF and/or Myfortic®) will be discontinued and they will be monitored for 10 years thereafter, for the appearance of allosensitization using panel reactive antibody (PRA) levels and monitor the persistence of elevated PRA levels. Primary objective is to determine the rate of allosensitization in patients 3 years after failed islet transplantation (i.e. stimulated c-peptide <0.3mg/mL) and monitor the persistence of elevated PRA levels (≥ 20%) at year 3, 6, and 9. Timing, frequency and level of change in PRA will be monitored after all immunosuppression is discontinued.

Inclusion Criteria:

1. History of at least one islet alone transplant (ie islet transplant in the absence of any other organ transplant).

Exclusion Criteria:

1. Inability to provide written informed consent.
2. Mentally unstable and/or unable to comply with the procedures of the study protocol.
3. History of any solid organ transplant.

Ages 18-75 years old that received at least one IT. Participants will be obtained from the pool of islet transplant recipients transplanted at the Diabetes Research Institute at the University of Miami, Miller School of Medicine.