CD163 (Cluster of Differentiation 163), also known by several other names including M130, p155, RM3/1, Ki-M8, Ber-MAC3, SM4, and GHI/61, is a type I transmembrane glycoprotein that is a member of the scavenger receptor cysteine-rich (SRCR) super family class B (1-3). CD163 is expressed specifically on the monocyte/macrophage lineage and has a theoretical molecular weight of 130-160 kDa in reducing conditions and 110 kDa in non-reducing conditions (2 - 6). CD163 is synthesized as 1076 amino acid (aa) protein consisting of a large extracellular domain (ECD) with nine SRCR domains, proline-serine-threonine rich (PST) linker domain, a transmembrane segment, and a cytoplasmic tail which has varying lengths depending on the isoform due to alternative splicing, with the short 49 aa form being the most common (1-3, 6).
One of the primary functions of CD163 is uptake of haptoglobin-hemoglobin (Hp-Hb) complexes from the liver, spleen, and bone marrow, ultimately triggering an anti-inflammatory response (3, 5, 7). CD163 also functions as an erythroblast adhesion receptor and promotes cell maturation and survival (3, 5, 7). Furthermore, CD163 functions in immune sensing of bacteria and as a receptor for tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) (3, 5, 7). As mentioned above, CD163 is expressed on cells in the monocyte/macrophage lineage and, in general, anti-inflammatory signals including glucocorticoids, interleukin (IL)-6, and IL-10 stimulate CD163 synthesis and expression while, conversely, pro-inflammatory signals such as interferon-gamma (INF-gamma), TNF-alpha, and lipopolysaccharide (LPS) downregulate CD163 (3, 5). In addition to membrane-bound form of CD163, the protein can be cleaved by metalloproteinases (MMP) and induced by LPS or phorbol myristate acetate (PMA) to release a soluble form (sCD163) into the plasma (7). Increased levels of sCD163 in the plasma and an increased number of CD163-expressing macrophages at the site of inflammation are associated with a variety of pathologies (3, 5-7). CD163/sCD163 is often increased and a suitable clinical marker for inflammatory diseases including rheumatoid arthritis (RA), Gaucher disease, chronic kidney disease, diabetes, and Crohn's disease (3, 5-7).
Alternative names for CD163 includes GHI/61, HbSR, Hemoglobin scavenger receptor, M130, macrophage-associated antigen, MM130, RM3/1, SCARI1, scavenger receptor cysteine-rich type 1 protein M130, sCD163, and soluble CD163.
1. Law, S. K., Micklem, K. J., Shaw, J. M., Zhang, X. P., Dong, Y., Willis, A. C., & Mason, D. Y. (1993). A new macrophage differentiation antigen which is a member of the scavenger receptor superfamily. European journal of immunology. https://doi.org/10.1002/eji.1830230940
2. Onofre, G., Kolackova, M., Jankovicova, K., & Krejsek, J. (2009). Scavenger receptor CD163 and its biological functions. Acta medica (Hradec Kralove).
3. Van Gorp, H., Delputte, P. L., & Nauwynck, H. J. (2010). Scavenger receptor CD163, a Jack-of-all-trades and potential target for cell-directed therapy. Molecular immunology. https://doi.org/10.1016/j.molimm.2010.02.008
4. Sulahian, T. H., Hogger, P., Wahner, A. E., Wardwell, K., Goulding, N. J., Sorg, C., Droste, A., Stehling, M., Wallace, P. K., Morganelli, P. M., & Guyre, P. M. (2000). Human monocytes express CD163, which is upregulated by IL-10 and identical to p155. Cytokine. https://doi.org/10.1006/cyto.2000.0720
5. Etzerodt, A., & Moestrup, S. K. (2013). CD163 and inflammation: biological, diagnostic, and therapeutic aspects. Antioxidants & redox signaling. https://doi.org/10.1089/ars.2012.4834
6. Skytthe, M. K., Graversen, J. H., & Moestrup, S. K. (2020). Targeting of CD163+ Macrophages in Inflammatory and Malignant Diseases. International journal of molecular sciences, 21(15), 5497. https://doi.org/10.3390/ijms21155497
7. Moller H. J. (2012). Soluble CD163. Scandinavian journal of clinical and laboratory investigation. https://doi.org/10.3109/00365513.2011.626868