= Transcytosis
<Transcytosis> carries material through a <biological cell> from one surface to another by combining <endocytosis>, intracellular <vesicle> transport and <exocytosis>. In an epithelial sheet, cargo can enter at the apical surface facing a cavity and leave at the basal or lateral surface facing underlying <tissue>. This route crosses the <cell> rather than passing through the gap between neighbouring <cells>.
An illuminating example is transfer of maternal <antibodies> across the intestine of a newborn rat. <Richard Rodewald> followed <antibodies> carrying an electron-dense ferritin label, and independently followed antibodies recognizable by a peroxidase reaction. <Electron microscopy> located tracer at the apical surface, in internal tubular <vesicles> and near release sites at the opposite surface. Experiments used isolated, ligated intestinal segments and control tracers to distinguish selective transport from leakage between <cells>. The observations establish a route across the epithelial <cell>, not merely disappearance from the intestinal cavity.<Intestinal transport of antibodies in the newborn rat by Richard Rodewald>[1973, abstract and Discussion, pp. 202–204]{ref}
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