Figure 2. The specific ablation of PrPC expression only on FDC blocks prion replication in the spleen. CD21-cre mice can be used to study FDC-specific gene function.40 (A and B), Using this approach we recently created a compound transgenic mouse in which PrPC expression could be specifically “switched off” only on FDC.10 (C&E), Following peripheral prion exposure high levels of PrPSc accumulate upon the surfaces of FDC in the spleens of control mice. (D&F) However, prion replication is blocked in the spleens of mice in which PrPC expression was specifically “switched off” only on FDC. Arrow heads in D show scavenged PrP within TBM. Arrows in E show PrPSc-positive FDC in the spleens of control mice. A&B, scale bar = 100 µm; C&D, scale bar = 20 µm; E&F, scale bar = 500 µm. Adapted from McCulloch et al.10