To further investigate the role of various blood components in prion disease transmission, we intracranially (IC) inoculated genetically susceptible VRQ/ARQ and ARQ/ARQ sheep with inocula composed of CD11c+ B1 lymphocytes, CD68+macrophages, or platelet-rich plasma derived from clinically ill sheep infected with the US no. 13–7 scrapie agent [27]. Here, CD68 is linked to prion disease.