Antitumor Immunity of Gut and the Role of Oral Immunotherapy in the Multidisciplinary Treatment of Digestive Organ Cancer

Associated with the gut is a broad immune system, and the various tissues which make up this system are termed gut-associated lymphoid tissue (GALT) which includes lymph nodes, the appendix, lymphoid nodules , Peyer's patches, intraepithelial lymphocytes, and lamina propria lymphocytes (16) . GALT is thought to play an important role in the immunological surveillance system against micoorganisms or dietary antigens entering the gut . GALT also appears to play an important role in the antitumor immunity of the gut , because natural killer (NK) cells and T cells are widely distributed in the epithelium and lamina propria of the gut. However, the role of GALT against digestive organ cancer is still unclear (1, 6). GALT works independently of systemic lymphoid tissue and has some important characteristics, such as a secretory immunoglobulin system, a homing phenomenon of T and B blasts, and induction of a tolerance to orally administered antigens. The most important phenomenon is that the local immunity of the gut is established by oral immunization, but not by systemic immunization (4, 15) .