Immune Responses to Microbial Polysaccharides
Darran J. Wigelsworth, Erin B. Troy and Dennis L. Kasper
from: Bacterial Polysaccharides: Current Innovations and Future Trends (Edited by: Matthias Ullrich). Caister Academic Press, U.K. (2009)
The immune system is capable of recognizing almost any biological polymer (including proteins and glycolipids) and presenting it to T cells via major histocompatability proteins. These adaptive immune responses have long been considered the territory of antigenic proteins, whereas carbohydrates are considered T-cell-independent antigens and are not recognized by the complete adaptive machinery. However, recent work reveals a larger role for sugars in immune recognition. The zwitterionic polysaccharide PSA from the commensal organism Bacteroides fragilis has recently been added to the list of antigens presented to T cells. This molecule has been shown not only to be presented on MHCII but also to play a role in immunomodulation and suppression of inflammatory diseases such as colitis. Bacteria have developed polysaccharide capsules to take advantage of the fact that polysaccharides are generally not recognized by the human immune system. However, the recent finding that sugars play a role in immune recognition makes them more attractive targets in the search for antigenic epitopes. This chapter will discuss in detail the immune response to foreign antigens, the function of zwitterionic polysaccharides in immune recognition, and finally the use of carbohydrates in glycoconjugated vaccines, undoubtedly one of the biggest scientific breakthroughs of the past century read more ...