It is of great interest that some substances in foods can
open tight junctions between IECs. When the capsianoside
contained in a sweet pepper was added to the apical side of a
monolayer formed by the human IEC line Caco-2, the tight
junctions transiently opened, followed by a drop of electric
resistance between the apical and basal sides (9). While the
tight junction basically acts as a barrier to pathogens or toxic
substances in the intestine, the transient opening of tight
junctions may be so important that antigens can be captured by
dendritic cells in the intestinal lamina propria and immune
responses to these antigens are efficiently evoked (10).