In this study, sensitized renal transplant recipients, who present an increased risk of acute rejection, will be evaluated for the benefit of quadruple immunosuppression, adding sirolimus to the traditional scheme with tacrolimus, mycophenolate, and prednisone.

Inclusion Criteria:

• Sensitezed renal transplant recipients with reactivity panel of antibodies (PRA) greater than 30% who agree and sign the consent form.

Exclusion Criteria:

• Obese patients (body mass index above 35 m2);
• History of GESF or membranoproliferative glomerulonephritis (MPGN) as primary cause of renal failure;
• Proteinuria (protein/creatinine ratio) greater than 0.5 mg/dL at the time of initiation of Sirolimus;
• Triglyceride levels greater than 300 mg/dl at enrollment;
• Active infection by hepatitis B virus, hepatitis C virus or HIV;
• CMV nonreactive IgG sorology at the time of transplantation.