C3AR is a single chain protein of 482 aa, with seven membrane-spanning regions and a molecular weight of 54 kD. C3AR is expressed by neutrophils, eosinophils, mast cells, monocytes, and dendritic cells. There are reports of C3AR expression in non-immune cells such as hematopoietic and mesenchymal stem cells as well as epithelial and endothelial cells. C3AR is coupled to heterotrimeric G proteins and after C3a binding, the signal transduced, results in chemotaxis, granule enzyme release and superoxide anion production.