| Abstract: | The complement system is involved in the antibacterial defence either with a delay, following the specific antibody response, or immediately through a direct interaction between complement components and the bacterial cell wall. Several gram- bacteria initiate the classical pathway through direct interaction between C1 and the lipid A of the lipopolysaccharides; this activation depends upon the structure, the accessibility and the state of polymerization of the lipopolysaccharides. Gram+ and gram- bacteria are able to activate the alternative pathway through a covalent C3b binding. Capsules appear to prevent activation due to their high content of sialic acid, which probably accounts for the virulence. As targets, bacteria may undergo opsonization mainly by C3b, or lysis through transmembrane channels formed by terminal components from C5b to C9. |
