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.
What are monoclonal antibodies?
identical antibodies produced in large quantities in the lab, complementary to a specific antigen
What does “mono” and “clonal” mean in monoclonal antibodies?
“Mono” means one, and “clonal” means identical, indicating identical antibodies produced from one type of cell.
Name three main uses of monoclonal antibodies.
- Medical treatment of cancer
- medical diagnosis
- pregnancy tests.
How is direct monoclonal antibody therapy used to treat cancer?
Antibodies bind to cancer cell antigens, blocking signals that trigger uncontrolled cell division, preventing tumor growth.
Why is direct monoclonal antibody therapy advantageous?
The antibodies only bind to cancer cells, minimizing harm to normal cells.
What are polyclonal antibodies?
mixture of different antibodies that recognize multiple epitopes on an antigen
What is an antigen
a molecule (often a protein) that triggers an immune response, specifically recognized by antibodies
How are monoclonal antibodies produced?
Using hybridoma technology, where B-cells from an animal are fused with myeloma cells to create hybrid cells that produce specific antibodies in large quantities.
Why are animals used in monoclonal antibody production?
they are immunized with an antigen to stimulate the production of B-cells that produce specific antibodies
What is a hybridoma cell?
A hybrid cell formed by fusing a B-cell with a myeloma cell
What is direct monoclonal antibody therapy?
Using monoclonal antibodies to block receptors on cancer cells, preventing cell division without harming normal cells
What is indirect monoclonal antibody therapy?
Attaching cytotoxic drugs to monoclonal antibodies that kill cancer cells when antibodies bind to the tumor.
How are monoclonal antibodies used in pregnancy tests?
They detect the presence of the hormone hCG in urine, producing a visible line if the hormone is present.
What is the nickname for indirect monoclonal antibody therapy?
Bullet drugs
Why is the production of monoclonal antibodies considered ethically controversial?
It involves the use of animals, often resulting in their death, raising concerns about animal welfare
What are the disadvantages of monoclonal antibody production?
- High production costs
- time-consuming processes
- ethical concerns regarding the use of animals.
Which animal organ is used to produce monoclonal antibodies, and what happens to the animal?
The spleen is used, and the animal (usually a mouse) is sacrificed
What is the role of the control band in pregnancy tests?
To ensure the test is functioning, a second immobilized antibody binds to unbound mobile antibodies
How do pregnancy tests work?
- Urine passes through reaction zone.
- HCG hormone binds to the mobile HCG antibody.
- Passes up the stick and HCG hormone binds to the
immobilised HCG antibodies in the results zone - Antibodies which do not attach to HCG
- Bind to antibodies in control zone
- Blue dye appears in both control and results zones (to show positive result)
