Kidney transplantation has improved survival and quality of life for patients with end-stage organ failure. Despite dramatic improvements in short-term survival, long-term survival of renal allografts has changed little during the past decade. Recently, it has been demonstrated that chronic lesions originate already very early after transplantation and that subclinical rejection (SCR) in protocol biopsies is a risk factor for late graft loss. However the efficacy of high-dose corticosteroids and other therapies for the treatment of SCR have been shown to be inadequate. Thus, despite the availability of a range of available medications there remains a need for therapeutic alternatives because patients may not respond to existing therapeutic choices, they do not show an improvement of the fibrosis reaction or an effect on long term survival, or they may develop immunosuppression induced serious (sometimes fatal) side effects and toxicities.