Defence Mechanisms and Phagocytosis Flashcards
What is a phagocyte?
a type of white blood cell, which carries out phagocytosis and destroys pathogens
Why is phagocytosis a non-specific defence mechanism?
as the phagocyte has multiple different receptors that can detect different pathogens. It does NOT have a single receptor that is only complementary to one pathogen.
Outline the process of phagocytosis
- Phagocyte is attracted to chemicals (toxins) released by the pathogen
- Phagocyte binds to chemicals on the surface of the pathogen
- The phagocyte engulfs the pathogen to form a phagosome
- lysosomes fuse to the phagosome, and release lysozymes (hydrologic enzymes) that hydrolyse the pathogen
What are 4 types of cell that can be recognised by the immune system?
- abnormal cells
- cells from a different organism of the same species
- toxins
- pathogens
How is the body able to recognise self-cells?
In a fetus;
- many lymphocytes in the blood
- collide almost exclusively with self cells, as there is no infection due to protection from the placenta
- any lymphocytes which have receptors that fit the shape of self cells will be destroyed or suppressed
- this leaves lymphocytes that can almost exclusively recognise non-self cells
Describe the roles of lysosomes in phagocytosis
fuse to phagosome and release lysozymes that hydrolyse the pathogen
What is a pathogen?
a microorganism that causes disease/an immune response
Describe how a pathogen is destroyed in phagocytosis…
- Phagocyte attracted by a substance / recognises (foreign) antigen;
- (Pathogen)engulfed /
- Enclosed in phagosome;
- fuses / joins with lysosome;
-Lysosome contains enzymes;
-Pathogen digested / molecules hydrolysed
What is an antigen?
- foreign protein
- that stimulates an immune response
What is an antigen-presenting cell?
a cell that displays an antigen, including infected cells and phagocytes
