FIG. 4.
PrPSc accumulation and infectivity titers in the spleen 70 days after i.p. injection with scrapie. Immunoblots show the accumulation of detergent-insoluble, relatively proteinase-K-resistant PrPSc. Treatment of tissue in the presence (+) or absence (−) of proteinase K before electrophoresis is indicated. Following proteinase K treatment, a typical three-band pattern was observed between molecular mass values of 20 and 30 kDa, representing unglycosylated, monoglycosylated, and diglycosylated isomers of PrP (in order of increasing molecular mass). Scrapie infectivity titers are expressed as log i.c. ID50 units per gram. Mice were treated with hu-Ig (control) or huTNFR:Fc 5 days before (a) or 14 (b) or 38 (c) days after scrapie injection. Lane M contained molecular mass markers. d, days; PK, proteinase K.