1 Cells And The Immune System Flashcards
1
Q
How is each type of cell specific?
A
Each type of cell has specific molecules on its surface that identify it. These molecules include proteins and enable the immune system to identify: pathogens, cells from other organisms of the same species, abnormal body cells, and toxins.
2
Q
Define antigen.
A
Molecule, usually proteins, that can generate an immune response when detected by the body. Usually found on surface of cells.
3
Q
Describe the effect of antigen variability on disease and disease prevention.
A
- antigens on surface of pathogen activate primary response.
- when infected 2nd time with same pathogen which has same antigens, they activate secondary response
- some pathogens can change their surface antigens, this antigen variability is called antigenic variation.
- means when infected 2nd time, memory cells produced from first infection will not recognise different antigens so immune system has to carry out primary response.
- primary response takes time to get rid of infection
- antigenic variation also makes it difficult to develop vaccines against some pathogens.
4
Q
Describe phagocytosis of pathogens
A
- phagocyte recognises foreign antigens on pathogen.
- cytoplasm of phagocyte engulfs pathogen
- pathogen now contained in phagocytic vacuole in cytoplasm of phagocyte
- lysosome fuses with phagocytic vacuole. Lysozymes break down pathogen.
- phagocyte then presents pathogens antigens to activate other immune system cells.
5
Q
Describe the difference between active and passive immunity.
A
- active requires exposure to antigen whereas passive doesn’t
- active takes a while for production to develop whereas passive is immediate
- active, memory cells produced whereas passive they aren’t
- active protection is long-term because antibody is produced in response to complimentary antigen being present in body. Whereas passive protection is short-term because antibodies given are broken down.
6
Q
How does the use of vaccines provide protection for individuals.
A
- vaccines contain antigens, may be free or attached to a dead or attenuated pathogen, that cause body to produce memory cells against particular pathogen, without pathogen causing disease.
- vaccines protect individuals, because they reduce occurrence of disease, those not vaccinated also less likely to get disease because fewer people to catch it from. This called herd immunity.
7
Q
Describe the structure of HIV.
A
- core contains genetic material (RNA) and some proteins.
- outer coating of protein called capsid.
- extra outer layer called envelope, made of membrane stolen from cell membrane of a previous host cell.
- loads of copies of an attachment protein sticking out from envelope that help HIV attach to host helper T-cell
8
Q
Explain how HIV replicates inside its host’s helper T-cells.
A
- attachment protein attaches to receptor molecule on cell membrane of host helper T-cell.
- capsid released into cell, where it uncials and releases genetic material into cells cytoplasm
- inside cell, reverse transcriptase is used to make complementary strand of DNA from viral RNA template.
- from this, double stranded DNA is made and inserted into human DNA.
- host cell enzymes used to make viral proteins from viral DNA found within human DNA.
- viral proteins assembled into new viruses, which bud from cell and go on to infect others.
9
Q
Explain how HIV causes symptoms of AIDS
A
- HIV infects helper T-cells, which act as host cells for virus. Without enough helper T-cells immune system is unable mount an effective response to infections because other immune system cells don’t behave how they should.
- people infected with HIV develop AIDS when helper T-cell numbers in body reach critically low level.
10
Q
Explain why antibiotics are ineffective against viruses.
A
- antibiotics kill bacteria by interfering with their metabolic reactions. Target bacterial enzymes and ribosomes used in those reactions.
- bacterial enzymes and ribosomes different to human ones. Antibiotics designed to only target bacterial ones so don’t damage human cells.
- viruses don’t have own enzymes and ribosomes, so because human viruses use human enzymes and ribosomes to replicate, antibiotics can’t inhibit them.
11
Q
Describe the ethical issues associated with the use of vaccines and monoclonal antibodies.
A
- vaccines tested on animals before humans
- testing vaccines on humans can be tricky. Eg. Volunteers may put themselves at unnecessary risk of contracting disease because they think they’re fully protected.
- some people don’t want to take vaccine due t risk of side effects, but still protected because of herd immunity- other people think unfair.
12
Q
Describe the ELISA (Enzyme-linked immunosorbent assay) test.
A
- tests allows you to see if patient has any antibodies to a certain antigen or any antigen to a certain antibody.
- used to test for:pathogenic infections, allergies.
- in test an antibody with an enzyme attached to it is used. This enzyme can react with substrate to produce coloured product. This causes solution in reaction vessel to change colour.
- colour change demonstrates that antigen or antibody of interest is present in sample.
13
Q
What are the 2 types of ELISA test.
A
- direct ELISA, uses single antibody that’s complimentary to antigen testing for.
- indirect ELISA , uses 2 different antibodies.
14
Q
Describe the use of monoclonal antibodies in targeting drugs to specific cell types.
A
- monoclonal antibodies can be made to bind to any target cell
- attach drugs to antibodies, which then bind to target cell
- drug and antibody will only bind to target cells, so side effects of antibody-based drug are lower than other drugs as accumulate near specific cells.
15
Q
Describe the use of monoclonal antibodies in medical diagnosis.
A
- monoclonal antibodies fixed to a plate
- sample added, if antigen present it forms antigen-antibody complex
- rinsed to remove unbound antigens
- some monoclonal antibody added with enzyme/colour attached
- rinsed to remove unbound antibodies
- observe to look for marker , if enzyme add substrate there’s colour change.
