Figure 4.

Sodium phosphotungstic acid (NaPTA) precipitation/western blotting analysis of lymphoreticular tissue samples for the presence of protease-resistant prion protein (PrP^res). Samples of tonsil (To), appendix (Ap), spleen (Sp) and lymph node (LN) homogenate, each corresponding to 50 mg of tissue, from the index case, were analysed alongside spleen samples (− and +) from a control case with a non-Creutzfeldt-Jakob disease (CJD) neurological disease. One of the latter control samples (+) had been spiked with brain frontal cortex homogenate from the index case corresponding to 300 µg of tissue prior to NaPTA precipitation. Brain frontal cortex homogenate from the index case (50 µg) and variant CJD frontal cortex homogenate reference standard (200 µg) were analysed directly, without prior NaPTA precipitation (FC and V, respectively). The molecular weight markers (M) are 40 kDa, 30 kDa and 20 kDa from top to bottom.