Arkitek Studios just wrapped in late January 2013 this new animation for Nature Immunology in London, describing what goes on in the mucosal lining ot the gut. Here's Nature Immunology's description:
The gut mucosa is the largest and most dynamic immunological environment of the body. It is often the first point of exposure to pathogens, and many microbes use it as a beachhead for access to the rest of the body. Therefore, the gut immune system needs to be ready to respond to pathogens, but at the same time it is constantly exposed to innocuous environmental antigens, food particles and commensal microflora that must be tolerated. Misdirected immune responses to harmless antigens are the underlying cause of food allergies and debilitating conditions such as inflammatory bowel disease. This animation introduces the key cells and molecular participants involved in gut immunohomeostasis and disease.