Mistletoe lectin transport by M-cells in follicle-associated epithelium (FAE) and IL-12 secretion in dendritic cells situated below FAE in vitro.

A galactose- and N-acetyl-D-galactosamine-specific lectin (Viscum album L. var. coloratum agglutinin, VCA), which is known for its anti-tumor activity, was isolated from Korean mistletoe. Mistletoe preparations have been given subcutaneously because of the unstability and poor absorption in the GI tract. In this study, we investigated the effect of incubation time and glucose on the VCA transport across the in vitro model of human FAE (follicle-associated epithelium) by two different cell models: Caco-2 cell monolayers mimicking human enterocytes and a model of the human FAE which is mainly composed of M-cells and enterocytes. As a result, the VCA transport across the FAE monolayer cells was higher and faster than the transport across the Caco-2 monolayer cells, and glucose increased VCA transport across both monolayer cells. In addition, IL-12 was secreted from myeloid DC1 and lymphoid DC2.4 cells which were co-treated simultaneously with LPS and VCA. Furthermore, the FAE model associated with underlying immune cells was established and VCA was added to the inserts apically. There was a greater IL-12 secretion in dendritic cells situated below FAE monolayer than Caco-2 monolayer. The results from this study provide important insight into the possible oral application of mistletoe on anti-tumor therapeutics.