Mucosal systems

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. 

In transdermal or mucosal systems, povidone, particularly the medium and high-molecular types, can be used as an bioadhesive, to improve or to control transdermal absorption [535, 571, 658], or to stabilize active ingredients or to... 

Thiolated polymers, also termed thiomers, are conventional mucoadhesive polymers chemically modified to contain a cysteine residue in the polymer chain and thus establish covalent disulfide bonds with mucin." They can be manufactured to be either cationic (mostly thiolated chitosans) or anionic (carboxylic acid-containing polymers) however, their mucoadhesive extent will mostly be determined by their capacity to covalently bind to mucin. The polypeptide backbone of mucin can be divided into three major subunits tandem repeat array, carboxyl-, and amino-terminal domains. While the amino-terminal domain contains some of the cysteine residues, the carboxyl-terminal domain contains more than 10% of the cysteine residues. These cysteine-rich regions are responsible for forming the large mucin oligomers and ultimately, the groups that allow for the covalent mucoadhesive bond formation with oral mucosal systems." ... 

P. Occhipinti and P. C. Griffiths, Quantifying Diffusion in Mucosal Systems by Pulsed-Gradient Spin-Echo NMR , Adv. Drug Deliver. Rev., 2008, 60, 1570. 

The development of oral vacdnes for stimulation of mucosal immunity is an important goal because of the simplidty of administration. The mucosal system is the first barrier a pathogen has to penetrate, and mucosal immunity is based on the production of IgA antibodies. The oral polio vaccine was an early example. The types of vacdnes used for oral dosage are the same as those available for administration by injection. Formulation of oral vaccines presents a particular challenge for the pharmacist and is likely to see major progress in the future. 

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