Replication of the Factor in Scrapie Material That Causes a Decrease in Polymorphonuclear Neutrophils

Abstract

Previous work has shown that homogenates of brain from mice infected with scrapie contain a factor that reduces the percentage of polymorphonuclear neutrophils (PMNs). In the present work, the titer of this factor was found to be approximately 10⁶ times greater than the infectivity titer for scrapie. The PMN factor replicated 10⁹-fold in mice that never showed signs of scrapie disease, i.e., mice inoculated with approximately 6 × 10⁻⁴ ld₅₀ units of scrapie. Inoculation of mice with 10¹² units of the PMN factor, which had been produced in the absence of scrapie infectious units, failed to cause scrapie disease.