Many newly formed T lymphocytes leave the small intestinal mucosa via lymphatics.

The results show that 50% of the IgA+ and 25% of the IgM+ cells that leave the gut are newly formed BrdU+ cells. However, in absolute numbers the BrdU+Ig+ lymphocytes are the smaller cell pool in the afferent lymph, 2 to 3 times more newly formed T cells were observed. The function of this unexpectedly large pool of newly formed T lymphocytes in oral immunity or tolerance has to be clarified. In a recent study Dunkley and Husband reported that non-B cells play an important role for the localization of plasma cell precursors in the lamina propria of the mucosa. So far it is unknown where the pool of newly formed T and Ig+ lymphocytes comes from. Partially they are produced in the PP. However, they may have their origin in the lamina propria of the mucosa as well as in other organs of the body. Further studies are necessary to characterize the origin and the function of the large numbers of newly produced T lymphocytes in the intestinal lymph.