Encouraged by these findings, we processed a blinded “test” plate containing 96 samples (Supplementary Table 1, opaque symbols in Fig. 1) comprising FR and FF pairs of known prion disease appendix samples, and FFPE samples from known controls (“PrP-negative”) and those of uncertain prion disease status with abnormal PrP immunoreactivity in follicular dendritic cells of the lymphoid follicle (“PrP-positive”). The gene discussed is PRNP; the disease is prion disease.