Topic 2 - The immune system Flashcards
What are antigens ?
The immune system
Molecules, usually proteins, found on the surface of the cell that can generate an immune response when detected by the body.
What’s an antibody ?
The immune system
A protein that’s specific to an antigen. They’re secreted by plasma cells
What are antibodies made of ?
The immune system
- 2 light and 2 heavy polypeptide chains.
- which are joined by disulphide bridges. Each antibody has 2 identical binding sites at the variable region.
- The variable region is determined by the sequence of amino acids.
- The constant region is the binding site for receptors.
What do immune system cells identify ?
The immune system
pathogens, abnormal body cells, toxins and cells from different organisms of the same species.
What are pathogens ?
The immune system
organisms that cause disease.
What’s the four steps in an immune response ?
The immune system
1.Phagocytosis
2. T-cells
3. B-cells
4.plasma cells
What’s a phagocyte ?
The immune system
A type pf white blood cell that carries out phagocytosis
What’s the first stage of an immune response ?
The immune system
phagocytosis:
1.A phagocyte recognises the foreign antigens on a pathogen.
2. The cytoplasm of the phagocyte moves around the pathogen, engulfing it.
3. The pathogen is now contained in a phagosome.
4.A lysosome containing hydrolytic enzymes fuses with the phagosome and forms a phagolysosome.
5. The enzymes hydrolyse the pathogen.
6. The phagocyte presents the pathogens antigens - sticking them on its surface to activate other immune cells.
How is a T-cell activated ?
The immune system
It has receptor proteins on its surface that bind to the complimentary antigens presented to it by phagocytes. This activates the T-cell.
What are two types of T-cells ?
The immune system
helper T-cells (TH cells)
cytotoxic T-cells (Tc cells)
What’s the role of helper T-cells ?
The immune system
- Their cell surface receptors bind to the foreign antigen.
- They release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells
- They also help activate b-cells, which secrete antibodies.
What is the role of cytotoxic T-cells ?
The immune system
- Kill abnormal and foreign cells.
- Make holes in the cell surface membrane using perforins, this makes the cell membrane become freely permeable and the cell dies
What is the role of B-cells ?
The immune system
- When the antibody on the b-cells’ surface meets a complimentary antigen it binds.
- This and the substances released from the T-cells activates the B-cell: clonal selection.
- Activated B-cells then divide into plasma cells: clonal expansion.
What’s the role of plasma cells ?
The immune system
- They’re identical clones of B-cells
- they secrete lots of antibodies monoclonal antibodies specific to the antigen.
- They bind to the antigens on the pathogens surface and form lots of antigen-antibody complexes.
- Antibodies have 2 binding sites meaning they can bind to 2 pathogens at once, meaning that pathogens clump together - agglutination.
- Phagocytes then bind to the antibodies and phagocytose many pathogens at once, leading to the destruction of the antigen carrying pathogens.
What forms the cellular response ?
The immune system
T-cells and phagocytes
What forms the humoral response ?
The immune system
B-cells, clonal selection and the prodction of monoclonal anitbodies.
What is the primary response of the immune system ?
The immune system
- When an antibody enters the body for the first time it triggers an immune response:
- The response is slow because there are limited numbers of B-cells that produce the anitbody.
- Eventually the body will produce enough correct antibodies to overcome the infection.
- Meanwhile the infected person will develop syptoms.
- After being exosed to an anitgen, both T-cells and B-cells produce memory cells which remian in the body for a long time.
- Memory T-cells remember the specifc antigen and will recognise it a second time round.
- Memory B-cells remember the antibdoes needed to bind to the anitgen.
- The person is now immune and their immune system will reponse quicly to a second infection.
What is the secondry response of the immune system ?
The immune system
- If the same pathogen enters the body again the immune system will recognise the antigens and produce a faster and stronger reposne:
- Clonal selection happens faster, memory B-cells ( which remeber the right anitbodies that are needed to bind to the antigens) are activated and divide into plasma cells that produce the complimentary antibodies.
- T memory cells(which remember and recognise the anitgen) are activated and divide to produde the correct T-cells to kill the antigens.
- The pathogen is often killed before you show syptoms.
What are vaccines ?
The immune system
- antigens that are free or attached to a weakened pathogen that can be injected or orally taken.
- it causes the body to produce memory cells against the disease without causing the disease.
- you develop immunity without getting symptoms.
What is herd immunity
The immune system
both the unvaccinated and vaccinated are protected as the overall occurrence of the disease is reduced so the unvaccinated are less likely to catch the disease.
what is a disadvantage of taking vaccines orally
The immune system
the enzymes in the gut may break down the antigens.
the molecules may be too big to be absorbed into the bloodstream
why are booster vaccines given
The immune system
to ensure that memory cells are produced
what is antigenic variation
The immune system
pathogens change their surface antigens due to gene mutations.
why is antigenic variation a problem
The immune system
memory cells to the other strain of the virus do not recognise new strains so new vaccines have to be developed.
what happens one a vaccine is published to the government
The immune system
the government and health authorities implement a programme of vaccination
what is active natural immunity ?
The immune system
the immune system makes its own antibodies after catching the disease naturally. this creates immunity.
what is active artificial immunity
The immune system
the immune system makes its own antibodies after being given a vaccine. this creates immunity.
what is passive natural immunity
The immune system
a baby becomes immune as it is given antibodies that have been made by its mother, given by the placenta or breast milk
what is passive artificial immunity
The immune system
you become immune after becoming injected with antibodies from someone else, e.g. for tetanus.
what are the differences between active and passive immunity
The immune system
- active required exposion to the antigens, passive does not.
- active takes a while for protection to develop, passives protection is immediate
- active produces memory cells, passive does not.
- active immunity is long term as memory cells are produced passive immunity is short term as the antibodies are broken down and memory cells are not produced.
Why do phagocytes present antigens
The immune system
sticking them on its surface to activate other immune cells.
How can monoclonal antibodies attack cancer cells ?
The immune system
- Cancer cells have antigens on their surface called tumour markers.
- monoclonal antibodies can be made which will bind to the tumour markers.
- Anti-cancer drugs can be attached to these antibodies and when the antibodies come into contact with the cancer cells they bind to the markers and kill the cell.
Why are the side effects for cancer cell targeting lower than other anti-cancer drugs
The immune system
The drugs accumulate near specific cancer cells
how do pregnancy tests work
Monoclonal Antibodies
- The application area contains mobile HCG antibodies with blue beads bound to them.
- When the urine is applied to the application area, if HCG is present it binds to the antibodies with the blue beads forming an antigen antibody complex and moves up the strip in the urine to the test strip.
- This contains more HCG antibodies which are stationary.
- The HCG and blue beads will bind to the antibodies showing a positive result.
- The control zone will bind any antibodies that have not been attached to hCG and shows the test is working.
What does an ELISA test do ?
Monoclonal Antibodies
it tests for the presence of a specific antigen or antibody
How does HIV/AIDS lead to death ?
HIV
HIV attacks T helper cells, these cells are apart of the immune system. therefore AIDS leads to disrupted immune response
What type of genetic material does HIV have ?
HIV
RNA
What is HIV’s lipid envelope made of ?
HIV
the membrane of the previous host cell
How does HIV replicate ?
HIV
- The attachment proteins attach to the receptor cells on the Host T-Cells membrane.
- The capsid is released into the cell, it un-coats and releases its RNA using integration.
- Inside the cell, reverse transcriptase is used to make a complimentary strand of DNA from the viral RNA template
- Viral dna is inserted into the human DNA. host cell enzymes are used to make viral proteins from viral dna.
- The proteins are assembled into new viruses which buds from the cell and go onto effect other cells
Why does antibiotics not work on HIV
HIV
- They dont have bacterial structures.
How do antiviral drugs work
HIV
most antiviral drugs target the virus specific proteins
For example reverse transcriptase inhibitors.
How can HIV be prevented
HIV
Having protected sexual intervourse
not sharing needles
why are viruses known as non living
Theyre not made of cells
they do not independently respire
they have no cell surface membrane
