Transcytosis plays a central role in the immunological functions of ep
ithelia, including the sampling of antigens that enter the body via th
e digestive, respiratory and urogenital tracts and their presentation
to underlying lymphoid tissues, the secretion of specific immunoglobul
ins required for the immune protection of mucosal surfaces and the tra
nsfer of maternal immunoglobulins to the fetus or newborn, providing t
he latter with passive immunity for the first weeks of independent lif
e.