Cell recognition and the immune system Flashcards
What is a pathogen?
an organism that causes infectious/communicable disease e.g bacteria, virus, fungi and protists
What are antigens?
Proteins (glycoprotein) on the surface of the cell membrane which initiate an immune response
What do pathogens do to cause disease?
destroy host cells, produce and secrete toxins,
What do antigens allow immune systems to recognise?
- foreign cells
- cells from the same species/ tissue
- abnormal body cells e.g tumours
- toxins
When does an immune response occur?
When the body is infected by a foreign body
What are the two types of immune responses?
non-specific (non memory) and specific (memory)
What are 3 types of white blood cells?
- phagocytes (non-specific)
- t-lymphocytes (specific)
- b-lymphocytes (specific)
What line of defence are the white blood cells?
Second (pathogen has to get past physical barriers)
What is another name for a phagocyte that carries out phagocytosis?
macrophage
Where are phagocytes found?
In the blood and in tissues
What is a non-specific response?
A response where any non-self cell that is detected will trigger the same response to destroy it (not specific to an antigen)
What can trigger an immune response?
-Pathogens
-Cells from other organisms e.g. transplants
-Cancerous cells
-Cells infected by a virus
-Injected antigens e.g. vaccines
-Our own cells if autoimmune disease
Describe the non specific response:
1.Phagocyte binds to foreign antigen of pathogen and phagocytosis occurs creating a phagosome.
2.Lysosome containing lysozyme enzymes fuses with phagosome and hydrolyses pathogen.
3.Breakdown products are absorbed by phagocyte and antigens can be presented on cell membrane…
What is HIV?
retrovirus that causes AIDS (Acquired immune deficiency syndrome)
How can HIV enter the body?
- Sharing needles (blood)
- Sexual fluids (sperm, vaginal fluids)
- Breast milk
- Blood during childbirth
Where do viruses replicate?
In the host cell
Why can’t viruses be destroyed by antibiotics?
Have different mechanisms to replicate and no cell wall, like bacteria, and therefore cannot be destroyed by antibiotics.
What does the structure of another labelled virus look like?
What does the structure of a labelled virus look like?
How is HIV replicated in helper T-cells?
- HIV is transported around in the blood until it attaches to a CD4 protein on the helper T cells.
- The HIV protein capsule then fuses with the helper T cell membrane, enabling the RNA and enzymes from HiV to enter.
- The HIV enzyme reverse transcriptase copies the viral RNA into a DNA copy and moves to the helper T cell nucleus, this is why it is called a retrovirus.
- Here mRNA is transcribed, and the helper T cell starts to create viral proteins to make new viral particles.
When does AIDS occur?
- Replicating viruses in the helper T cells interfere with their normal functioning of the immune system.
- Host is unable to produce adequate amount of immune response so body is susceptible to infections.
What are the symptoms of AIDS?
- Very low number of helper T- Ls meaning inability to activate B-ls
- Increased susceptibility to secondary infections of lungs or brain
What is the Elisa test for HIV?
- Testing strip contains HIV antigens
- Blood added to sample
- If HIV antibodies present , they bind to test strip
- First wash removes blood
- Add secondary antibody complementary to first antibody
- Second wash to remove second antibody + enzyme
- Add dye that changes colour in presence of enzyme
- Colour change= positive test
What are antibodies?
proteins with a specific binding site that is complementary in shape to a particular antigen.
