Exploiting M cells for drug and vaccine delivery.

The specialised antigen sampling M cells represent an efficient portal for mucosal drug and vaccine delivery. Delivery may be achieved using synthetic particulate delivery vehicles including poly(DL-lactide-co-glycolide) microparticles and liposomes. M cell interaction of these delivery vehicles is highly variable, and is determined by the physical properties of both particles and M cells. Delivery may be enhanced by coating with reagents including appropriate lectins, microbial adhesins and immunoglobulins which selectively bind to M cell surfaces. Live attenuated microorganisms are also suitable as vaccines and mucosal vectors and many, including Salmonella typhimurium, innately target to M cells. After cell surface adhesion, delivery vehicles are rapidly transported across the M cell cytoplasm to underlying lymphoid cells and may subsequently disseminate via the lymphatics. Further definition of M cell development and function should permit exploitation of their high transcytotic capacity for safe and reliable mucosal delivery.