CR2 and scrapie: C1qa−/− mice and CD21−/− mice succumbed to scrapie with an attack rate of 100% (C1qa−/− mice: n = 4, 288±26 dpi; CD21−/− mice: n = 10, 235±24 dpi) (Figs. 6A–C), with CD21−/− mice succumbing to scrapie slightly earlier when compared to C1qa−/− mice.