Most abdominal aortic aneurysms (AAA) are covered by an intraluminal thrombus (ILT), which contains erythrocytes among other components. Hemolysis of erythrocytes releases hemoglobin, which forms reactive oxygen species (ROS) that have a damaging effect on the vessel wall. To prevent this, hemoglobin is bound to haptoglobin, taken up via the surface receptor CD163 and degraded by the antioxidant enzyme heme oxygenase‑1 (HO-1). The induction of the CD163-HO‑1 system is a feature of M_Hem macrophages, the role of which has already been demonstrated in connection with arteriosclerotic diseases. In AAAs, CD163-positive cells are mainly found in areas with increased iron deposition and CD163 expression increases during the course of the disease until AAA rupture. Furthermore, an increase in CD163 is associated with an increase in a number of protective antioxidant genes, such as HO‑1. In addition, an increase in soluble CD163 and HO‑1 has been found in serum and plasma samples from AAA patients. Further studies are needed to investigate whether the increased expression of components of the CD163-HO‑1 system in AAA can counteract local inflammation, iron-related ROS production and prevent disease progression.