Double immunolabeling of leukocyte subsets and PrPScin the hemal nodes and retropharyngeal lymph nodes from scrapie-infected sheep. Retropharyngeal lymph nodes (A, C, E, G) and abdominal hemal nodes (B, D, F, H) were immunolabeled with T lymphocyte-specific (CD3; animal ID 4496; A and B), B lymphocyte-specific (CD79a; animal ID 4496; C and D), macrophage-specific (CD163; animal ID 4489; E and F) and follicular dendritic cell-specific (120 kDa antigen; animal ID 3776; G and H) Abs along with anti-prion F99/97.6.1 mAb. Under these double labeling conditions, PrPSc appears in red while each cell-type appears in brown. Enlarged pictures of co-labeled cells with cell-type specific mAb and PrPSc are inserted into the right lower corner of each panel. Scale bar = 50 μm.