The causes of deterioration of transplanted kidney function are poorly understood. The purpose of this study is to determine the disease processes that cause transplanted kidney dysfunction and loss in patients who received a kidney either recently or over a year prior to entering this study. This study will also identify specific characteristics in kidney transplant recipients that predict whether a kidney transplant will be successful.

Over time, chronic kidney graft dysfunction progressively threatens the long-term survival of a kidney graft. The disease processes behind graft dysfunction are unclear. However, chronic kidney graft dysfunction is likely to be caused by certain definable factors. Such factors may include collagens III and IV, transforming growth factor (TGF)-beta, T and B cell surface markers, cell cycle proteins, fibronectin, and laminin. Determining what disease processes and which specific factors are most responsible for kidney graft dysfunction may help in designing future interventional trials for kidney transplant patients. The purpose of this study is to determine whether clinical, laboratory, and histologic studies at the time of initial graft dysfunction will clarify the processes and factors that lead to deterioration and loss of a kidney graft. This is an observational study that will enroll participants who have recently received kidney transplants (prospective cohort) and participants who have had kidney transplants for a longer period of time and are now experiencing kidney graft dysfunction (retrospective cohort).

The duration of this trial may differ between participants, depending on when deterioration of kidney graft function occurs. Participants will be followed until graft loss or death. There are no exclusive study visits associated with this study. Study data are gathered from routine laboratory follow-up tests completed at the participant's local medical center and from information obtained at the time of kidney biopsy. Participants may need to undergo a kidney biopsy as clinically indicated. At the time of biopsy, participants will also undergo urine and blood collection.

Inclusion Criteria for Prospective Cohort:

• Received a kidney transplant within 10 days prior to study entry, on or after 10-01-2005
• Recipient of kidney or simultaneous kidney/pancreas with no additional transplant at the time of the kidney transplant

Inclusion Criteria for Retrospective Cohort:

• Received a kidney transplant before 10-01-2005
• Recipient of kidney or simultaneous kidney/pancreas with no additional transplant at the time of the kidney transplant
• Undergoes a clinically indicated kidney biopsy due to new onset deterioration of function, defined as having an increase in serum creatinine
• The creatinine level on or before 01-01-2006 must be 2 mg/dl or less OR the patient must have developed new onset proteinuria, defined as having a protein/creatinine ratio of 0.4 or more

Kidney transplant recipients