Imaging the Lymphatic System in Heart Transplantation and Its Immunological Implications

Cardiac transplantation is an important form of treatment for patients with end-stage heart failure. Rejection by the immune system of the recipient is a major cause of graft loss. The lymphatic system plays a crucial role in the immune response, but has not received much attention. Donor blood vessels are joined to those of the recipient during the transplant operation; however, due to their small size, donor lymphatic vessels are not reconnected. For this same reason the imaging of lymphatics, and therefore the understanding of this system, has been hampered. In recent years great strides have been made towards developing new imaging modalities that allow the lymphatic system to be imaged in a non-invasive or semi-­invasive manner. Not only does this imaging provide new insights into the lymphatic system, it also presents the possibility of using lymphatic imaging to diagnose and monitor diseases and their treatment. In the case of heart transplantation, which will be the focus of this chapter, the lymphatic system has been shown to play a role in the alloimmune response. Imaging may be used as an extra tool for patient monitoring or as a research tool to develop new treatment protocols for recipients of cardiac transplants.