Question

How do phagocytes eliminate pathogens? What group of pathogens are most easily phagocytosed and why?

Answer 1

Ans) Phagocytosis of human are termed as professional or non- professional cells depending on their phagocytosis. Phagocytosis is important for the human immunity as they protect the human body against the invading pathgen and the the dead cells of the body. The professional cells have receptors which distinguish them from  non-professional cells.This receptor of the  professional cells can bind to the respective pathogen. The pathogen secreate chemical agents which attracts the  professional cells to move towards them by the process of chemotaxis. The receptor of the  professional cells bind the pathogen and engulf it. There are various mode by which phagocyte destroy the pathogen. Those modes are by the process of oxidants and nitric oxide. Another mode is the fusing the lysosome with the phagosome where the pathogen is trapped and lysosome killed the pathogen.

The pathogens which are not capsulated and whose cell wall does not contain M protein and Waxes (Mycolic acid), and devoid of the enzyme Leukocidins, caogulase are easily phagocytosed.

The pathogen which contains capsulated are involved in the avoidance of phagocytosed mediated recognition.E.g. of Non capsulated bacteria are Corynebacterium, Neisseria.

The bacteria which does not have mycolic acid and M-protein in their cell are vulnerable to the phagocytosis.

Some enzyme like Leukocidins, caogulase have the ability to avoid the phagocytosis.

Leukocidins attack certain types of WBC’s

1. Kills WBC’s which prevents phagocytosis

2. Releases & ruptures lysosomes

lysosomes - contain powerful hydrolytic enzymes which then cause more tissue damage

Coagulase - cause blood to coagulate. Their activity are:-

Blood clots protect bacteria from phagocytosis from WBC’s and other host defenses

Staphylococcus aureus - are often coagulase positive