immunity Flashcards
what are antigens?
Molecules that can trigger an immune response. They are mainly proteins and are usually found on the surface of cells.
What is an implication of organ donation?
The donor would have different antigens to your antigens and so it can trigger an immune response which could lead to you rejecting the transplant.
what is a pathogen?
a disease causing microorganism.
outline the process of phagocytosis.
- phagocyte identifies the foreign antigen on pathogen
- the pathogen engulfs and ingests the antigen into the phagocytic vacuole
- lysosome fuses with the phagocytic vacuole
- lysosome releases lysozymes which hydrolyse pathogen
- phagocyte then presents the foreign antigen on its surface.
what are monoclonal antibodies?
- antibodies produced from a single group of plasma cells
- they’re specific to one antigen because their binding site has a unique tertiary structure
- that only an antigen with a complementary shape can fit into
what is an antibody?
proteins that bind to antigens to kill pathogens.
why do antibodies have 2 binding sites?
so 2 pathogens can bind and then be clumped together for agglutination
what makes a antibody specific?
the variable region
outline the cell mediated response
- phagocytosis present antigens on their surface
- receptors on T-helper cells fit exactly onto the antigens
- T-cells are activated to divide rapidly by mitosis and form clones of its self
- Cloned Tcells can;
1. form memory cells
2. stimulate phagocytosis
3. stimulate Bcells to divide and secrete their antibody
4. activate cytotoxic Tcells
what does the protein perofin do?
makes holes in the membrane so its more permeable
outline the humoural response
- Specific complimentary Bcells bind to the foreign antigen
- antigen enters the Bcell by endocytosis and gets presented on its surface
- T-helper cells bind to antigens and stimulate that same Bcell to divide by mitosis and make clones.
- clonal selection can make;
1. plasma cells - clones of Bcells
2. make monoclonal antibodies
3. agglutination - so phagocytosis of a lot of pathogens can occur at once
4. memory cells which can lead to a faster production of Bcells to be made the next time that pathogen invades
what do plasma cells do?
secrete antibodies into the blood plasma
- they are responsible for the immediate defence
- primary immune system
what do memory cells allow to happen?
a faster secondary immune response
what happens if the same pathogen enters again?
- a stronger, more faster immune response
- The memory Bcells can divide into plasma cells to produce the correct antibody
what is active immunity?
where the individual has memory cells and is able to make their own antibodies which provides long term immunity.
2 examples of active immunity are?
- naturally = primary infection
2. artificially = by vaccination
what is passive immunity?
Where the individual is given antibodies. These work then die so there no long term immunity and no memory cells are made.
2 examples of passive immunity are?
- Naturally - the mother can give it to the baby by the placenta/breast milk
- Artificially - Injection
what is a vaccination?
a dead or weakened form of pathogen that carry antigens which are able to stimulate the immune response.
this leads to the production of antibodies and memory cells.
what are the problems with vaccinations?
- don’t always work
- side effects
- many strains of pathogen and we cant get them all therefore we cannot always achieve heard immunity.
- antigenic variability
what is herd immunity?
where large amounts of the population are vaccinated and most people are immune.
what is the benefit of herd immunity?
it increases the chance of a non-immune person coming into contact with an immune person, the pathogen then has no where to go and dies out.
what is antigenic variation?
- where the pathogen mutates and changes shape.
- the memory cells are no longer complimentary and so they do not recognise the pathogen and the pathogen can reharm
what happens in pregnancy tests?
- the HCG binds to complementary antibodies which are bound to blue beads, forming an antigen-antibody complex
- the test strip has antibodies to HCG that are stuck
- the HCG-antibody complex then binds to the antibodies that are stuck which forms the blue line.
(not pregnant = nothing binds)
what does the ELISA test allow you to do and what is it used for?
- it allows you to see if a patient has any antibodies to a certain antigen
- it is used for medical diagnosis’ such as HIV and allergies
- there’s a colour change which demonstrates that the antigen or antibody being tested is present.
what is DIRECT ELISA?
- antigens from sample are bound inside of a well in a well plate.
- complementary antibodies are added
- the well is washed to remove any unbound antibodies
- substrate solution is added
- if detection antibody is present, the enzyme reacts with the substrate and there’s a colour change
- colour change = positive result
what is INDIRECT ELISA?
- HIV antigen bound to the bottom of the well
- blood plasma added
- if HIV antibodies are present, they’ll bind
- wash out any unbound antibodies
- a secondary antibody with a specific enzyme is added to the well = binds to the specific HIV antibody
- wash out any unbound antibodies
- substrate solution is added - this is able to react with enzyme attached to secondary antibody
- colour change - HIV is present
what are the ethical issues of using monoclonal antibodies?
animal cells are used to produce them and some people disagree with this
what is HIV?
human immunodeficiency virus
what does HIV do and what are the symptoms?
infects and kills helper Tcells which are host cells and attacks the immune system
flu like symptoms
what is AIDS?
acquired immunodeficiency syndrome
what are the complications of AIDS?
- there’s the risk of opportunistic infections which are serious infections that kill the patient
- the HIV/AIDS don’t kill themselves
what is reverse transcriptase and what is it used for?
- enzyme
- to make complementary strand of DNA from viral RNA template strand
outline HIV replication
- attachment protein attaches to receptor molecules on the cell membrane
- capside is then released into the cell which uncoats and releases RNA into the cell
- reverse transcriptase makes complementary strand of DNA from RNA template
- it gets inserted into the human cell
- the host cell enzymes make viral proteins from viral DNA from within the human DNA
how do antibodies work?
antibiotics kill bacteria by interfering with metabolic reactions
why don’t antibiotics work on viruses?
because they use human host cells and antibiotics cant attack human cells
There is no cure/vaccine for HIV.
How can you reduce its spread?
- have protected sex
- be careful with bodily fluids
- if the mother is pregnant and she is HIV positive then give her antiviral drugs
