C5AR1 and rheumatoid arthritis: C5a and C5AR1 have also been associated with disease processes such as ischemia-reperfusion injury, rheumatoid arthritis, asthma, immune complex diseases, neurodegeneration and Alzheimer's disease (Klos et al., 2009; Guo and Ward, 2005; Farkas et al., 2003; Huber-Lang et al., 2001a; Woodruff et al., 2008).