Structure of the Gram-negative bacterial cell wall and the activation of the immune system

Gram-negative bacteria are covered by cells membrane, peptydoglycan and outer membrane. Outer membrane contains phospholipids, outer membrane proteins (OMPs) and lipopolysaccharides (LPS). The possibility of activation of innate system by bacterial cell structures depends on the structure and organisation of bacterial outer membrane. Sialic acid not a common component in bacteria has been found in O-specific region of LPS, of some serotypes, as a component of the capsular polysaccharide of envelope and plays an essential role in protecting Gram-negative bacteria against bactericidal activity of serum. Molecular mimicry is called as structural, serological and functional homology and similarity between microbial antigens and host tissue. This homology is considered as important pathogenic factor involved in several autoimmune diseases. Molecular mimicry of host structures by bacterial lipopolysaccharides, capsules and outer membrane proteins has been reporter to contribute to the pathogenesis of certain bacteria.