This region contains several genes, including those encoding FcγRII, the complement receptor CR1/2 (CD35/CD21), and the decay-accelerating factor CD55 (Prodeus et al. 1998; Bolland and Ravetch 2000; Miwa et al. 2002; Wu et al. 2002), which have each been implicated in the causation of SLE when inactivated by gene-targeting in 129 embryonic stem cells. The gene discussed is CR1; the disease is systemic lupus erythematosus.