Abstract

In its evolution as a stalwart defense against microbes, the human immune system has developed a profound ability to differentiate self from nonself, presenting the major barrier to the long-term success of organ transplantation. Multiple nonimmunologic factors contribute to the immune response to the allograft in thoracic transplantation. For the most part, these nonimmunologic factors result in activation of the innate immune system that exacerbates the adaptive immune response, initiating a cascade of allograft antigen-specific immune-mediated mechanisms of injury. The scope and type of immune-mediated injury then causes allograft damage, leading to allograft dysfunction. Understanding basic principles of immunology provides the foundation for tissue typing aimed at minimizing alloreactivity and estimating the risk of antibody mediated rejection (AMR). Pharmacologic immunosuppression with various types of medications aims to mitigate the allograft response while limiting side effects and opportunistic infections. Although treatment of acute rejection (AR) is effective, AMR remains difficult to treat, and little can be offered to mitigate chronic rejection, limiting the long-term effectiveness of thoracic transplantation to treat end-stage heart or lung disease.