M-CELL - THE MAIN ENTRANCE OF THE MUCOSAL IMMUNE-SYSTEM

M cells are higly specialized cells within the follicle-associated epi thelium (FAE) of the respiratory and intestinal tracts. They play a ce ntral role in the induction of the mucosal immune response by transpor ting antigens to the lymphoid tissue. In this way the immune system ma y encounter the limitless variety of antigens that enter the body thro ugh the gut and airways. Here we describe the structure and the functi on of intestinal M cells. In addition, controversial issues relating t o the M cell biology, such as APC function and the origin of M cells w ithin the FAE, are discussed.