What is the mechanism of action of azathioprine before and after renal transplantation?

Inhibits DNA : Azathioprine (aza) is a nucleoside analogue that inhibits dna production. It affects rapidly proliferating cells such as b cells and t cells and thus is an immunosuppression agent. In transplantation aza has mostly been replaced by the similar but more efficacious agent Mycophenolic Acid sold as cellcept (mycophenolate mofetil). Both aza and CellCept (mycophenolate mofetil) are used with other immunosuppression agents and are not used alone.