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Post-transplant lymphoproliferative disorder (PTLD) is the name given to a B-cell proliferation due to therapeutic immunosuppression after organ transplantation. These patients may develop infectious mononucleosis-like lesions or polyclonal polymorphic B-cell hyperplasia. Some of these B-cells may undergo mutations which will render them malignant, giving rise to a lymphoma. In some patients, the malignant cell clone can become the dominant proliferating cell type, leading to frank lymphoma, a group of B cell lymphomas occurring in immunosuppressed patients following organ transplant. ==Causes== The disease is an uncontrolled proliferation of B cell lymphocytes latently infected with Epstein-Barr virus. Production of an interleukin-10, an endogenous, pro-regulatory cytokine, has also been implicated. In immunocompetent patients, Epstein-Barr virus can cause infectious mononucleosis in adolescent, which is otherwise asymptomatic in children during their childhood. However in immunosuppressed transplant patients, the lack of T-cell immunosurveillance can lead to the proliferation of these EBV-infected of B-lymphocytes. However, calcineurin inhibitors (tacrolimus and cyclosporine), used as immunosuppressants in organ transplantation inhibit T cell function, and can prevent the control of the B cell proliferation. Depletion of T cells by use of anti-T cell antibodies in the prevention or treatment of transplant rejection further increases the risk of developing post-transplant lymphoproliferative disorder. Such antibodies include ATG, ALG and OKT3. Polyclonal PTLD may form tumor masses and present with symptoms due to a mass effect, e.g. symptoms of bowel obstruction. Monoclonal forms of PTLD tend to form a disseminated malignant lymphoma. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Post-transplant lymphoproliferative disorder」の詳細全文を読む スポンサード リンク
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