Mucosal immune system

Castro, G.A. and Amtzen, C.J. (1993) Immunophysiology of the gut a research frontier for integrative studies of the common mucosal immune system. American Journal of Physiology G599-G610. 

The main site of the mucosal immune system in the gut is referred to as gut-associated lymphoid tissue (GALT), which can be divided into inductive and effector sites. In the small intestine, the inductive sites are in the Peyer s patches, which consist of large lymphoid follicles in the terminal small intestine. The contact with external antibodies triggers a series of cascade events in the body based on immune response (Brandtzaeg et al., 1999). 

Brandtzaeg P., Baekkevold E.S. and Farstad I.N. (1999). Regional specialization in the mucosal immune system what happens in the microcompartments Immunol Today, 20, 141-51. 

Nagura H. and Sumi Y. (1988). Immunological functions of the gut-role of the mucosal immune system . Toxicol Pathol, 16(2), 154—164. 

McGhee, J.R. et al., The Mucosal Immune System from Fundamental Concepts to Vaccine Development, Vaccine. 10, 75, 1992. 

The induction of an immune response by various mucosal routes is an important approach for the control of mucosally acquired infections. The apparent linked nature of the mucosal immune system enables the delivery of an antigen to any mucosal surface to have the secondary effect of potentially inducing immunity at others. Induction of a combination of systemic and secretory immune responses can be determined by the nature of the antigen, the route of administration, and the delivery system utilized. For example, traditional parenteral vaccines primarily induce IgM and IgG responses, whereas mucosal vaccination can elicit both IgG and secretory IgA responses (Corthesy, 2007). 

This chapter first provides a description of immunity in general and then more specifically, immunity in the mucosal immune system. The immune response of both intestinal and respiratory tracts will be described in detail as these are the two most common portals of targeted vaccine development for mucosal immunity. The chapter will cover the basis of mucosal immunity using plant-based oral vaccines. Strategies for increasing mucosal immunity, such as the use of adjuvants, will also be discussed. Finally, the chapter will cover the precliiucal tests and various cliiucal trials that are taking place with respect to production of human and veterinary therapeutic proteins in plants. 

The common mucosal immune system (CMIS) is now well established as a separate component of the host s immune apparatus, quite distinct from and independent of the systemic immune system described above. Moreover, if an immune response is induced at one site in the mucosal system this generally leads to responses at distal mucosal sites of the CMIS, presenting a potentially large advantage. It should be noted that there are approximately 6 x 1010 antibody producing cells in mucosal tissues and 2.5 x 1010 lymphocytes in the entire lymphatic system. 

Mucosal immunization prevents pathogens from infiltrating or infecting the body whereas systemic immunization resolves an infection after the invasion has occurred, thereby suppressing the disease. There is also clear evidence that both systemic and mucosal immunity is induced by mucosal immunization. As noted earlier, there is also evidence that immunization at a single site in the body can result in protection of the entire mucosal system so there must be some form of communication between sites and this justifies the term common mucosal immune system. 

Table 1. Major tasks being fulfilled by the mucosal immune system... 

Nevertheless, there is also accumulating evidence that a certain regionalization exists in the mucosal immune system, in particular a dichotomy between the gut and the upper respiratory tract. Differences in the antigenic repertoire, adhesion molecules or chemokines involved in leukocyte extravasation might explain this disparity. Primed immune cells may tend to home to the effector sites corresponding to the inductive sites, where the initial antigen contact took place. Such regionalization within the common mucosal immune system has to be taken into account in the development of certain mucosal vaccines [11]. 

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McGhee, J.R., et al. 1992. The mucosal immune system From fundamental concepts to vaccine development. Vaccine 10 75. 

Nochi, T. and Kiyono, H. (2006) Innate immunity in the mucosal immune system. Curr. Pharm. Des. 12,4203-4213. 

Neutra M.R., Phillips T.L. and Phillips T.E. (1984). Regulation of intestinal goblet cells in situ, in mucosal explants and in the isolated epithelium. Ciba Found. Symp. 109, 20-39 Nguyen T., Chin W-C. and Verdugo P. (1998). Role of Ca2 + /K+ ion exchange in intracellular storage and release of Ca2+. Nature 395, 908-912 Nochi T. and Kiyono H. (2006) Innate immunity in the mucosal immune system. Current Pharmaceutical Design 12,4203 1213... 

Galdeano, C. M. and Perdigon, G. (2006). The probiotic bacterium Lactobacillus casei induces activation of the gut mucosal immune system through innate immunity. Clin. Vaccine Immunol. 13(2), 219-226. 

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