Macrophages provide the first line of defence against pathogens and can be found in virtually all tissues and organs of the body, except in blood vessels. These vessels must thus be protected from injury and pathogens by other cells, still unidentified. In this project, we aim to characterize a novel population of macrophages that we found in the blood vessels and are atypically produced by endothelial cells forming the vessel walls, hence we termed them endothelial macrophages (eMΦ). Our preliminary data suggests that eMΦ phagocytose bacterial particles and dying or faulty cells in the blood. Characterizing eMΦ and their precise role in physiological and non-physiological conditions will provide novel insights into the protection mechanisms of blood vessels and blood. Tailoring eMΦ to combat pathogens or cancerous cells present in the blood could be part of future immunotherapy strategies.