RAG1-/-and all splenocyte donor mice were infected with 3610 6 PFU of MNV1.CW3 p.o. in 25 ml of cDMEM. All other mice were infected with 3610 7 PFU MNV1.CW3 p.o. In RAG1-/-mice two segments of the small intestine were harvested: a one inch section of the small intestine immediately distal to the pylorus of the stomach, (designated the duodenum/jejunum), and a one inch section of the small intestine immediately proximal to the cecum (designated the distal ileum). In all other mice the distal ileum and three mesenteric lymph nodes (MLN) were harvested. With the exception of RAG1-/-mice (inoculated at 4-6 weeks of age) and aged WT mice (inoculated at 14 months of age), all other mice were inoculated at 6-10 weeks of age.