Fewer PrPc myeloid-based cells in sheep with the prion-resistant genotype

Numerous sheep with the prion gene (PRNP) that encodes for 171QQ develop scrapie, a neurodegenerative prion disease of sheep. Relatively few cases of scrapie-affected sheep with PRNP genetics that encode for 171RR, however, have been found. Using flow cytometric analysis, statistically fewer PrPc-positive microglia and monocytes were observed from sheep with 171RR PRNP genetics than from sheep with 171QQ PRNP genetics (P<0.05). One possibility for the lack of PrP(Sc) accumulation in brains and lymph nodes of scrapie-exposed sheep with 171RR PRNP genetics is because of fewer PrPc-positive myeloid-derived cells available for conversion of PrPc to PrP(Sc).