Abstract
The historical aspects, nomenclature, morphology, location within the epithelium, proliferation kinetics and lifespan, thymus-derived and bone marrow-derived lymphocyte populations, lymphocyte traffic, factors which influence the numbers of lymphocytes, current theories of the function of lymphocytes and clinical application of lymphocyte counts of the intraepithelial lymphocytes of the small intestines of humans, rats and mice were reviewed.