Immunity Flashcards
Describe how a phagocyte works:
1) A phagocyte recognises foreign antigens on a pathogen.
2) The cytoplasm of the phagocyte moves round the pathogen engulfing it.
3) The pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte.
4) A lysosome fuses with the phagocytic cackle.The lysozymes break down the pathogen.
5) The phagocyte then presents the antigens of the pathogen on its surface to activate other immune system cells.
How does phagocytosis activate helper T cells?
receptors on a specific helper T cell fit exactly onto the antigens that phagocytes display.
What do activated T cells do?
- produce cytokines
- these cytokines stimulate T cells to divide rapidly by mitosis and form a clone of genetically identical cells.
What can clones T cells do?
- stimulate B cells to divide and secrete their antibody.
- stimulate phagocytes to engulf pathogens by phagocytosis.
- Develop memory cells that enable a rapid response to future infections by the same pathogen.
What can cloned T cells differentiate into and what do these cells do?
-they can differentiate into cytotoxic T cells which produce a protein called perforin that makes holes in cell membranes; the perforated cell becomes permeable to all substances and the cell dies.
What are plasma cells and what do they do?
Plasma cells are clones of B cells.They secrete antibodies which are specific to the antigens.
Explain how antibodies work:
They bind to antigens on on the surface of the pathogens to form lots of antigen-antibody complexes.
Antibodies have two binding sites so can bind to two pathogens at the same time.This means that pathogens become clumped together- this is called agglutination .
Phagocytes can then bind to the antibodies and phagocytose many pathogens at once.This process leads to the destruction of pathogens carrying this antibody in the body.
What makes up the cellular immune response?
T-cells and the immune system cells they interact with e.g phagocytes
What makes up the humoral immune response?
B-cells, clonal selection and the production of monoclonal antibodies from the humoral response.
Describe how vaccines work:
Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen without without the pathogen causing disease.This means you become immune without getting symptoms.
Explain antigenic variation:
1) Some pathogens can change their surface antigens.
2) This means when you are infected for a second time the memory cells produced from the first infection will no recognise the antigens so the immune system has to start from scratch.
-Antigenic variation makes it difficulty to develop vaccines.
What is active immunity?
This is the type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen.
What is passive immunity?
The immunity you get from being given antibodies from a different organism-your immune system doesn’t produce any of its own.
natural- the baby gets it through the placenta/breast milk
Artificial- e.g injection of someone else’s blood
Describe how monoclonal antibodies are used to target drugs to a particular cell type:
1) cancer cells have antigens called tumour markers that are not found on normal body cells.
2) monoclonal antibodies can be made that will bind to the tumour markers.
3) you can attach anti-cancer drugs to the antibodies.
4) when antibodies come into contact with cancer cells they ill bind to the tumour markers
5) this means the drug will only accumulate where there are cancer cells, this means the side affects are lot less using antibody based drugs.
Describe how monoclonal antibodies are used on pregnancy tests:
1) the application area contains antibodies for hCG bound to a coloured bead (blue)
2) When urine is applied to the application area any hCG will bind to the antibody on the beads forming an antigen-antibody complex.
3) The urine moves up the stick to the test strip, carrying any beads with it.
4) the test strip contains antibodies to hCG that are stuck in place.
5) If there is any hCG present the test strip turns blue because the immobilised antibody binds to any hCG- concentrating the hCG-antibody complex with the blue beads attached.If no hCG is present, the beads will pass through the test area without binding to anything and so it won’t go blue.
