This study will test the safety and effectiveness of a combination of three drugs followed by long-term treatment with just one drug in preventing organ rejection in kidney transplant patients. Current anti-rejection medicines are not completely effective in preventing rejection. This trial will test how well Thymoglobulin, Tacrolimus, and Sirolimus work together post-transplant and if the treatment can be reduced over time to control rejection with either Tacrolimus or Sirolimus alone.