C3.2.5 Infection control by phagocytes Notes

Infection Control by Phagocytes

1. Imagine you cut your finger while gardening.
2. Within hours, the area becomes red and swollen.
3. This is your immune system springing into action, with phagocytes, specialized white blood cells, leading the charge.
4. Phagocytes are a crucial component of the innate immune system and play a vital role in defending the body against infection.
5. These cells recognize, engulf, and digest pathogens through a process known as phagocytosis.

Amoeboid Movement: How Phagocytes Reach the Battlefront

1. Phagocytes, like macrophages and neutrophils, are not confined to blood vessels. They move to infection sites using amoeboid movement.
2. Amoeboid movement is a crawling-like motion that allows cells to navigate through tissues.
3. The process works as so:
   1. Chemotaxis: Phagocytes detect chemical signals from damaged tissues or pathogens.
   2. Diapedesis: They squeeze through capillary walls into tissues.
   3. Pseudopodia: Extensions of the cell membrane help them move toward the infection.

Recognizing and Engulfing Pathogens

1. Once at the infection site, phagocytes identify pathogens by detecting antigens on their surfaces.
2. Antigens are molecules that trigger an immune response.

Steps of Pathogen Recognition and Engulfment

1. Recognition: Phagocytes bind to antigens using receptors on their surface.
2. Engulfment: The cell membrane wraps around the pathogen, forming a vesicle called a phagosome.
3. Digestion: The phagosome merges with a lysosome, creating a phagolysosome. Enzymes inside the lysosome break down the pathogen.

Digestion by Lysosomal Enzymes