O-Antigen

O-antigen (syn. somatic antigen) is one of 32 antigens that make up the group of somatic antigens (O-group). It is one of the most common and important antigens in microbiology and immunology. O-antigens are polysaccharide chains that are found on the surface of bacteria.

O-antigens can be divided into three main types: A, B and C. Each of them has its own unique properties and functions. For example, O-antigens type A are the most common and include bacteria such as E. coli, Salmonella typhi and Shigella flexneri. Type B O-antigens include bacteria such as Yersinia pestis and Yersinia enterocolitica, and type C O-antigens include bacteria such as Vibrio cholerae and Vibrio parahaemolyticus.

The study of O-antigens is important for understanding the mechanisms of the body's immune response to bacterial infections. In particular, type A O antigens can cause an allergic reaction in people who are allergic to E. coli or other bacteria, including Salmonella.

Thus, O antigens are an important component of microbiology and are essential in understanding the immune response to bacterial infections and allergic reactions.