Abstract
Scrapie is a naturally occurring disease of domestic and wild sheep and goats. Like other Transmissible Spongiform Encephalopathies (TSE), scrapie is a chronic, invariably fatal neurodegenerative disease characterized by the
accumulation of the abnormal isoform of the host encoded prion protein (PrPsc). The involvement of the immune system is not yet clearly defined in scrapie pathogenesis. Following the inoculation via the skin in mice, a functional immune system is critical for the neuroinvasion since PrPsc is earlier immunodetectable in lymphoid tissues than in the brain of infected animals and SCID (severe combined immunodeficiency) mice seem to be refractory to the infection.
Immunohistochemistry is the current gold standard diagnostic technique for scrapie detection and in the absence of definitive data on the nature of the infectious agent, PrPsc immunodetection constitutes one of the main
methodologies for pathogenetic studies.
In our experimental model, 12 sheep have been subcutaneously inoculated in the drainage area of the prefemoral lymph node with scrapie infected brain
homogenized. The lymph nodes of the contralateral side were used as controls. Two sheep were inoculated in the same area with scrapie-free brain homogenized. The animals were culled and divided into 4 groups according to the scoring value of immunolabelling with PrPsc antibody in lymph nodes.
Spleen and distal jejunal lymph node, as well as right and left inguinal, popliteal, submandibular, and retropharyngeal lymph nodes were collected at necropsy and fixed in zinc-salt.
Using a panel of monoclonal antibodies (86D for γ/δ TCR; 7C2 for CD8+cells; 17D for CD4+cells and SW73.2 for MHC class II-bearing cells) the distribution and number of lymphocytes subsets and MHC class II positive mononuclear cells have been investigated and compared.
