The environment that normal mucosa of the gastrointestinal tract has is different from the environment of the normal lymph nodes. The normal uninfected lymph node doesn’t have antigen. However, the gut is loaded with bacteria. Whatever anatomy that is exposed to the outside environment such as the gastrointestinary tract and respiratory tract is where a specialized mucosal immune system has to be present. These tissues come in contact with antigen first; and are constantly exposed to antigen. Mucosal infections cause an extraordinary amount of infections and mortality world wide. Rapidly responding memory T-cells are found in the mucosal areas of the body and they are able to respond to antigens quickly.
There are effector T cells throughout the gastrointestinal tract. Cytotoxic CD-8 cells eliminate antigen throughout the gastrointestinal tract. Cytokines are responsible for recruiting the cytotoxic CD-8 cells to the gastrointestinal tract. IgA is also found in the gastrointestinal tract. It is responsible for only a moderate immune response. A lesser immune response is favored for the gastrointestinal tract since it contains acid-secreting cells, as well as serving as a mediator between the outside world and the inner systems of the body.