C5AR1 and Arthritis: In agreement, both genetic ablation or pharmacological inhibition of the C5a-C5aR axis improved arthritis or prevented the disease in animal studies (Wang et al., 1995; Goodfellow et al., 2000; Ames et al., 2001; Grant et al., 2002; Ji et al., 2002; Woodruff et al., 2002; Katschke et al., 2007; Banda et al., 2012).