Wnt signaling as master regulator of T lymphocyte responses: implications for transplant therapy.

T cell-mediated immune responses to the grafted tissues are the major reason for failed organ transplantation. The regulation of T cell responses is complex and involves MHC molecules on transplanted organs, cytokines, regulatory cells and antigen presenting cells. The evolutionary conserved Wnt signal transduction pathway has long been known for its importance in development of stem cells and immature T cells in the thymus. Recent evidence indicates the Wnt pathway as a master regulator of T cell immune responses via governing the balance between Th17/Treg and by regulating the formation of effector and memory cytotoxic CD8 T cell responses. In doing so Wnt signals influence the outcome of immune responses in transplantation settings.