Phagocytes Flashcards
What is phagocytosis?
A form of endocytosis where large particles (e.g. cell debris) are taken up into vesicles and are fused with a lysosome so degraded products are recycled if useful
What is a phagocyte?
Cels which can ingest particles from the surrounding
What is an antigen?
A molecule that stimulates an immune response
What is the immune response?
A specific response to a pathogen which involves lymphocytes and antibodies
What are types of non-specific defences?
Blood clotting, inflammation, wound repair and phagocytes
What is the purpose of blood clotting?
To seal off wound
What is the purpose of inflammation?
Histamine causes cells to release cytokines messenger molecules that increase inflammation and fever
What is the purpose of wound repair?
To regenerate tissues using collagen
What are types of phagocytes?
Neutrophils and macrophages
What are the goals of secondary defences?
Neutralise any toxins produced by pathogens, prevent pathogen multiplying, kill pathogen and remove any remains of pathogen
What are the 3 types of phagocytes?
Monocytes, macrophages and granulocytes
What are monocytes?
Not mature phagocytes
What are macrophages?
They are free or fixed
What are granulocytes?
Basophils, neutrophils and eosinophils
Where are neutrophils made?
In bone marrow
How do neutrophils move?
They travel in the blood and squeeze through tissues through capillaries so can rapidly exit into tissues
What is the lifespan of neutrophils?
They are short lived and are released in large names when an infection occurs and form pus when they die
What is the structure of neutrophils?
They have lysosomes and a very effective cytoskeleton
What can neutrophils respond to?
Histamine and cytokines
How are neutrophils attracted?
Damaged and infected cells release histamine and capillaries are leakier
What is the result of histamines?
More fluid causes swelling and more tissue fluid which washes pathogens into lymph nodes where macrophages wait
Where are macrophages made?
In bone marrow
How do macrophages move?
They are stationary or mobile so can travel in monocytes or settle in tissues (especially lymph nodes) and develop into macrophages
What is the lifespan of macrophages?
They are long lived
What is the function of macrophages?
They engulfed foreign pathogens and present antigens to lymphocytes (T-cells)
Where are dendritic cells found?
Tissues close to edge of body such as skin and gut
What is the function of dendritic cells?
They ingest pathogens and migrate to lymph nodes to display antigen
What are the stages of phagocytosis?
- Pathogens release chemicals that attract phagocyte.
- Phagocytes recognise non-self glycoproteins on surface of pathogens
- Binds to pathogen
4.
What is the process of antigen presentation?
- Digested pathogen fragments combine with MHC surface glycoproteins
- MHC-antigen complex displayed on surface of macrophages
- Now antigen presenting cell to T cells
What is MHC?
A cell surface protein used by vertebrates to recognise foreign molecules
How does MHC work?
It binds to peptide fragments from pathogens and displays for recognition by T cell
How many classes of MHC are there?
2
How do cytokines work?
The attraction more phagocytes to attract more WBC to increase body heat
What is the effect of antigens?
They stimulate an immune response
What happens in response to antigens?
The formation of antibodies and is recognised by the immune system as foreign to the body, a toxin is released by the pathogen and chemical markers on the outer membrane of pathogen
How are glycoproteins produced?
By lymphocytes
What is the purpose of glycoproteins?
They are released in response to an infection and identity and neutralise antigens
What is the shape antibodies?
Y shape
What is the structure of antibodies or immunoglobulins ?
Variable region which has different amino acids which form different shapes and has a specific shape which is complementary to 1 antigen
What is the same across all antibodies of a class?
The constant region
What are actions of antibodies?
Opsonins, agglutination and anti-toxin preparation
What do opsonins do?
They coat pathogen binding sites and tag them
What is the effect of opsonins?
The pathogen is unable to infect cell and phagocytes recognise antibodies and engulf pathogens
What is agglutination?
Large antibodies bind to many pathogens
What is the effect of agglutination?
Clump is too large to enter cells and is more likely to be phagocytosed
What is anti-toxin preparation?
Soluble toxins released by bacteria are precipitated out of solution
What is the effect of anti-toxin preparation?
Can be phagocytosed more easily
