Capsular Polysaccharide (CPS) / K Antigen
Capsular Polysaccharide (CPS) is associated with cell surface non-covalently and
protects bacteria from host immune system (Whitfield, 2002). The K antigen repeat units
form a high molecular weight structure called as 'capsule'. The antigen serotyping is
useful in understanding the pathogenesis and for epidemiological studies in tracing the
origin of disease.
Functions of Capsules include :
- Prevention of dessication
- Adherence
- Resistance to non-specific host immunity (complement and complement-mediated opsonophagocytosis
- Resistance to specific host immunity (Because these capsules are structurally similar to polysaccharides encounteres on host tissue, these capsules are poorly immunogenic, and elicit a poor antibody response in the host.)
- Mediating the diffusion of molecules through the cell surface ( The microbial proteins synthesized are transported outside the cell)