Because the T cell response is so powerful, all patients need to be on three different drugs that effect the T cell response in three different ways. Every patient must be on a glucocorticoid or steroid, an antimetabolite and a calcineurin inhibitor.
The glucocorticoid or steroid is often used in high doses immediately after transplantation and then reduced over time. The side effects including high blood pressure and diabetes are a major draw back.
The antimetabolite is often Mycophenolate Mofetil which affects the white cells and inhibts them from reproducing.
The calcineurin inhibitor is Cyclosporine or Tacrolimus. They both work on T cells too stop their reproduction but unfortunately they both cause kidney failure.
Only the use of all three of these types of drugs can allow the rejection response to be over powered.