Importance of local immunity in enteric infection.

Evidence suggests that protection against intestinal infections is mediated by an immune system that is unique in many ways. The predominant intestinal immunoglobulin differs in structure, function, and site of origin from those immunoglobulins found in the blood-stream. Cell-mediated intestinal immune responses also may arise separately from those of the rest of the body. Further studies are necessary to characterize the local immune response to many human bacterial, viral, and protozoal pathogens, and to clarify the mechanism of "homing" of immunocompetent cells to the large and small intestine, mammary glands, and other external mucosal surfaces.