Heart transplantation is the best option for patients with end-stage heart failure. Cardiac allograft vasculopathy (CAV) is the leading cause of death following cardiac transplantation and is not managed by current therapies. Its pathogenesis traduces in an accelerated form of coronary artery disease (CAD) with similarities to atherosclerosis but also particular features of endothelial dysfunction associated to the alloimmune conflict and humoral responses toward the graft. Intravascular ultrasound (IVUS) is the validated invasive method for late CAV diagnosis, but occurs lesions are established. Identification of reliable non-invasive early endothelial injury biomarkers that reflect mechanisms of cardiac damage thus remain a major challenge to optimize therapeutic management of post transplant morbidity. Endothelial dysfunction is a central feature of both CAV and CAD and results from a desquilibrium in the balance of endothelial lesion and repair that is partly controlled by recipient immune system. Through their expression of receptors sensing antibodies (FcR CD16) and endothelial stress-induced signals (CX3CR1 fractalkine receptor and NKG2D MICA receptors), Natural Killer (NK) cells represent effector cells with unique potential to generate both humoral and innate immune injury of graft endothelium.