Figure 2.

Possible routes of propagation of ingested prions. After oral uptake, prions may penetrate the intestinal mucosa through M cells and reach Peyer's patches as well as the enteric nervous system. Depending on the host, prions may replicate and accumulate in spleen and lymph nodes. Myeloid dendritic cells are thought to mediate transport within the lymphoreticular system. From the lymphoreticular system and likely from other sites, prions proceed along the peripheral nervous system to finally reach the brain, either directly via the vagus nerve or via the spinal cord, under involvement of the sympathetic nervous system.