Transport of Mistletoe Lectin by M Cells in Human Intestinal Follicle- Associated Epithelium (FAE) In Vitro

Purified mistletoe lectins are known to have cytotoxic and stimulating activities in the immune system. Mistletoe extract has been given subcutaneously because of its unstablity and poor absorption in the Gastrointestinal (GI) tract. A hallmark of M cells is their capacity to internalize material from the lumen and to transfer it efficiently to the underlying lymphoid cells. Although lectins are the prime candidates for oral vaccine delivery, the mechanisms whereby lectins are taken up, transported by M cells, and affect underlying immune cells remain poorly understood. In this study, uptake mechanism of Korean mistletoe lectin (Viscum album L. var. coloratum aggulutinin, VCA) across the human FAE (follicle associated epithelium) was investigated. An inverted FAE model of co-culture was obtained by a co-culture system of Caco-2 cells and human Raji B lymphocytes, and VCA transport across the in vitro model of human FAE was investigated. There was a greater transport of VCA across FAE monolayer cells than that of Caco-2 monolayer cells. These observations will be useful to assess the transport of other orally administered material in the GI tract.