The monoclonal antibody 20/70 recognizes the mouse receptor of C5a (CD88). Mouse anaphylactoxin complement factor C5a is a split product of C5, one of the most effective inflammatory chemokines, and interacts with two C51 receptors, C5aR and C5L2. Most C5a effects are mediated through C5aR. It is known that C5aR is essential in triggering acute inflammation. C5a receptors are seven transmembrane GTP-binding protein-coupled receptors, belonging to the rhodopsin supergene family. The 45 kDa C5a receptor is expressed by white blood cells, such as neutrophils, eosinophils, basophils, monocytes, dendritic cells, and mast cells. C5aR can be expressed on immune and non-immune cells. Non-immune cells expressing C5aR include vascular endothelial cells, cardiomyocytes and bronchial epithelial cells. C5aR signaling involves intracellular calcium mobilization and activation of protein kinase B (PKB) and protein phospholipase D (PLD) pathways. High C5aR expression levels have been associated with the pathogenesis of many inflammatory diseases, autoimmune and neurodegenerative diseases such as rheumatoid arthritis, multiple sclerosis, atherosclerosis and inflammatory bowel disease. The blockade of C5aR in the body greatly reduces inflammatory damage. The monoclonal antibody 20/70 has been used in functional studies and can prevent C5a from binding to its receptor.