Follicular Dendritic Cell-Specific Prion Protein (PrPc) Expression Alone Is Sufficient to Sustain Prion Infection in the Spleen
Figure 2
FDC-restricted PrPc expression in the spleens of Prnpstop/-→CD21-Cre Prnpstop/- mice.
A) The anticipated distribution of PrPC expression on FDC and B cells in tissues from each mouse group. B) The detection of Cre in the tail and spleen but not blood of the Prnpstop/-→CD21-Cre Prnpstop/- mice confirmed the restriction of the Cre-expression to the stromal but not haematopoietic compartments of these mice (upper panel). Efficient Cre-mediated recombination of Prnpstop (Prnpstop(R)) was restricted to the FDC-containing stromal compartment of the spleens of Prnpstop/-→CD21-Cre Prnpstop/- mice when compared to control mice. Cre-mediated recombination by CD21-expressing lymphocytes was efficiently prevented in these mice by the irradiation and transfer of Prnpstop/- bone marrow as demonstrated by the lack of a Prnpstop(R) band in DNA extracted from blood (lower panel). B, blood; S, spleen; T, tail; M, DNA size markers; a, b, c, control DNA samples for each transgene combination tested which were (a) Prnp-/-, (b) Prnpstop/- and (c) complete recombination of the stop cassette within the Prnpstop/- allele. C) IHC analysis of PrPC expression (blue) by FDC (CD35+ cells; red) and sympathetic nerves (TH+ cells, green) confirmed PrPC expression was restricted to FDC in spleens of Prnpstop/-→CD21-Cre Prnpstop/- mice. Scale bar, 100 µm. D) Morphometric analysis confirmed that the magnitude of the PrPC expression co-localized upon the surfaces of FDC in the spleens of Prnpstop/-→CD21-Cre Prnpstop/- mice was similar to that observed upon FDC in spleens from Prnp+/-→Prnp+/- control mice (p<0.690, n = 48 FDC networks/group). In contrast, in the absence of Cre-recombinase expression by FDC in CD21-Cre Prnpstop/-→Prnpstop/- mice, PrPC expression was substantially lower than that observed upon FDC in spleens from Prnp+/-→Prnp+/- control mice (p<1×10-25, n = 48 FDC networks/group). E) Morphometric analysis confirmed that PrPC expression upon the surfaces of sympathetic nerves in the spleens of Prnpstop/-→CD21-Cre Prnpstop/-, CD21-Cre Prnpstop/-→ CD21-Cre Prnpstop/- and CD21-Cre Prnpstop/-→Prnpstop/- mice was significantly ablated when compared to that observed upon sympathetic nerves in spleens from Prnp+/-→Prnp+/- control mice (p<1×10-25, n = 48 sympathetic nerves/group). For all panels n = 6 mice/group.