In: Biology
How do bacteria resist destruction by phagocytic cells?
Bacteria can resist destruction by phagocytic cells by following one of the mechanisms given below :
1) Avoidance of contact with Phagocytes - Bacteria may invade or remain confined in regions inaccessible to phagocytes, or they may avoid provoking an overwhelming inflammatory response. Some of the bacteria such as Streptococcal streptolysin or their products inhibit phagocyte chemotaxis. Others bacteria can cover the surface of the bacterial cell with a component which is seen as "self" by the host phagocytes and immune system. Such a strategy hides the antigenic surface of the bacterial cell.
2) Inhibition of Phagocytic engulfment - Resistance to phagocytic ingestion is usually due to a component of the bacterial cell surface (cell wall, or fimbriae, or a capsule. Some of the examples include Polysaccharide capsules of S. pneumoniae, Haemophilus influenzae, Surface slime of Pseudomonas aeruginosa etc.
3) Killing phagocytes before or after ingestion - Any of the substances that pathogens produce that cause damage to phagocytes have been referred to as aggressins. Most of these are actually extracellular enzymes or toxins that kill phagocytes. Phagocytes may be killed by a pathogen before or after ingestion.