Final answer:
Antibodies can overcome the defense of bacterial capsules by tagging them for phagocytosis, neutralizing their infectivity, and aiding in their clearance from the body. The specific binding of antibodies to bacterial antigens allows the immune system to more effectively recognize and eliminate the pathogen.
Step-by-step explanation:
The presence of antibodies in the body can neutralize and help overcome the defenses of bacteria with capsules. Bacterial capsules are structures that surround the cell wall, providing a slippery and difficult-to-engage surface that impedes phagocytosis. Antibodies, part of the adaptive immune response, are capable of binding to these capsules or other antigens on the bacterial surface. This action effectively 'tags' the bacteria for destruction, as the antibody-coated bacteria provide binding sites for immune cells such as phagocytes. The interaction between the Fc region of antibodies and phagocyte receptors triggers the internalization and breakdown of the pathogen through phagocytosis.
Bacteria can use proteases as virulence factors to degrade antibodies and evade this immune response. However, the presence of sufficient and specific antibodies can prevent bacteria from using their capsules effectively. Antibodies improve recognition by phagocytes, leading to the clearance of the extracellular pathogen. They can also neutralize pathogens by blocking key sites that enhance infectivity, preventing them from docking on host cells or entering and infecting them.
Aside from capsules, bacteria may use other virulence factors such as M proteins on Streptococcus fimbriae, mycolic acid in Mycobacterium tuberculosis, and antigenic variation, seen in pathogens like Borrelia burgdorferi and Neisseria gonorrhoeae, to evade the immune system. The presence of antibodies specific to the bacterial serotype allows for a better immune response and decreased chance for the bacteria to cause infection or disease.