The CD163:haptoglobin:hemoglobin complex is endocytosed (Schaer et al. 2006, Kristiansen et al. 2001) by monocytes or macrophages. CD163 is constitutively endocytosed by monocytes independently of ligand binding (Schaer et al. 2006). Upon endocytosis, the receptor?ligand complex enters early endosomes where haptoglobin:hemoglobin complexes are released from CD163. The receptor then recycles to the cell surface while haptoglobin:hemoglobin complexes continue through the endocytic pathway to end up in lysosomes where the protein moieties and the ligand are degraded.