CR2 and prion disease: In contrast, none of the mice with PrPC-ablated FDC (Prnpflox/-→CD21-Cre Prnpflox/- mice, n = 0/6; CD21-Cre Prnpflox/-→CD21-Cre Prnpflox/- mice, n = 0/7) succumbed to clinical prion disease during their life-spans (Table S1).