CD163 is a transmembrane scavenger receptor expressed on the macrophage surface. It has 9 B-type SRCR extracellular domains mediating serum haptoglobin clearing/endocytosis, pathogen binding and signal transduction, and calcium binding. CD163 is used as a surface marker of M2 type macrophages, including M2 type tumor associated macrophages (TAMs), which facilitate cancer progression by secreting cytokines to promote angiogenesis, immunosuppression and metastasis. Inflammatory stimulation and stress signal can induce extracellular domain shedding of CD163 to generate soluble CD163 (sCD163). The increased sCD163 level in serum is associated with low-grade inflammation in disease conditions.
