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Studies of a few last years give evidence for a role of apoptosis not only in graft rejection but also in induction of transplantation tolerance. Apoptosis – programmed cell death is an active process which refers to superflous and defective cells. For a responsiveness to allograft the most important are two mechanisms of apoptosis: AICD (activation induced cell death) which involves Fas/FasL engage- ment and PCD (passive cell death) – caused by cytokine withdrawal. Graft rejection is caused by genetic differences between a donor and a recipient. Allograft is damaged by effector cells including alloreactive lymphocytes T CD8+. These cells express FasL and could thereby induce apoptosis in Fas-positive graft cells. Participation of peripheral apoptosis in induction of transplantation tolerance depends on pool size of alloreactive lymphocytes – apoptosis is necessary to reduce the size of alloreac- tive T cells clone to be small enough to be controlled by immunoregulatory mechanism (“pool size” model). Apoptosis facilitates also the development of immunoregulation by antiinflamatory action and thereby suppression of immunostimulatory abilities of APC. Therapeutic strategies of the induction of transplantation tolerance by alloreactive lymphocyte deletion include macrochimerism, modification of FasL expression, costimulatory blockade, and anti-CD28 antibodies in the presence of IFN-γ. Most of immunosuppressive drugs like CsA and FK506 possibly inhibit apoptosis by inhibition of T cell activa- tion. It is quite likely that there are also regiments that induction of apoptosis contributes to their immunosuppressive activity, e.g. RAPA and MMF. Apoptosis of alloreactive lymphocyte T seems to be necessary to achieve transplantation tolerance. Not only does it reduce directly the quantity of cells attacking graft but it also facilitates the development of immunoregulation state.
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The Editorial Board
Andrzej Łukaszyk - przewodniczący, Zofia Bielańska-Osuchowska, Szczepan Biliński, Mieczysław Chorąży, Aleksander Koj, Włodzimierz Korochoda, Leszek Kuźnicki, Aleksandra Stojałowska, Lech Wojtczak

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