S100A8 and rheumatoid arthritis: RAGE is a member of the immunoglobulin superfamily of cell surface receptors and has been shown to play a role in the inflammatory processes underlying both RA and CVD; its activation occurs through binding of various proinflammatory ligands, notably the S100 protein family, including S100A8/A9 (calprotectin) and S100A12, both of which are overexpressed in RA and psoriatic arthritis (another autoimmune disease affecting the joints).