In vivo studies using properdin-deficient mice have revealed important roles for properdin in disease models including septic and non-septic shock (Ivanovska et al., 2008; Stover et al., 2008), various arthritis models (Dimitrova et al., 2010, 2012; Kimura et al., 2010), and abdominal aortic aneurism (AAA; Zhou et al., 2012). Here, CFP is linked to Arthritis.