The T cell as a bridge between innate and adaptive immune systems: Implications for the kidney. The immune system is classically divided into innate and adaptive components with distinct roles and functions. T cells are major components of the adaptive immune system. T cells are firmly established to mediate various immune-mediated kidney diseases and are current targets for therapy. Ischemic acute renal failure, a major cause of native kidney and allograft dysfunction, is mediated in part by inflammatory components of the innate immune system. However, recent data from experimental models in kidney as well as liver, intestine, brain and heart implicate T cells as important mediators of ischemia reperfusion injury. These data reveal new insights into the pathogenesis of ischemic acute renal failure, as well as identify novel and feasible therapeutic approaches. Furthermore, the identification of T cells as a mediator of early alloantigen-independent tissue injury demonstrates that the functional capacity of T cells spreads beyond adaptive immunity into the realm of the innate immune response.