sjdiugcsiufe Flashcards
What is a vaccine?
The injection of antigens from dead, weakened or inactive pathogens, stimulating a weak immune response, producing memory cells.
Suggest some points to consider when evaluating methodology relating to the use of vaccines and monoclonal antibodies.
- Was the sample size large enough to be representative?
- Were participants diverse in terms of age, sex, ethnicity and health status?
- Were placebo / control groups used for comparison?
- Was the duration of the study long enough to show long-term effects?
- Was the trial double-blind to reduce bias?
How do vaccines provide protection for entire populations against disease?
Herd Immunity - If a large proportion of the population is vaccinated, then the majority of people will not become ill from infection. This results in fewer infected people to pass the pathogen, and therefore unvaccinated people are less likely to come into contact with someone with the disease. This helps to protect vulnerable people such as young children and elderly people, as well as other people who do not get vaccinated due to personal or medical reasons.
What are the differences between active and passive immunity?
- In active immunity, the person is exposed to the antigen, either natural (via primary infection) or artificially (via vaccination), whereas in passive immunity, the person has not been exposed to the antigen.
- In active immunity, the antibodies were produced and secreted by the person’s own B-plasma cells, but in passive immunity the antibodies that are introduced into the body were produced by another organism (e.g. through breast milk)
- Active immunity is slower as it requires a full immune response. Passive immunity is much quicker as the antibodies can act immediately.
Describe the replication of HIV in helper T-Cells.
- HIV attachment proteins attach to receptors on helper T cell.
- Lipid envelope fuses with T-Helper cell-surface membrane, releasing capsid into cell.
- Capsid breaks down, releasing RNA and reverse transcriptase into the cell.
- Reverse transcriptase converts viral RNA to DNA.
- Viral DNA is inserted into helper T cell DNA, so it is replicated when cells replicate.
- DNA is used to make HIV RNA and proteins at the host ribosomes.
- Virus particles are assembled, which bud off from the cell membrane and continue infecting other cells.
Name the 3 main ways that HIV can be transmitted
- Having unprotected sex with an infected person.
- Close contact with the blood of an infected person (via the sharing of needles for drug use or the use of infected blood in blood transfusions)
- Mother to child (Shared through the placenta or through breast milk).
Suggest some points to consider when evaluating data relating to the use of vaccines and monoclonal antibodies.
- What side effects were observed, and how frequently did they occur?
- Was a statistical test used to see if there was a significant difference between start & final results?
- Was the standard deviation of final results large, showing some people did not benefit?
- Did standard deviations of start & final results overlap, showing there may not be a significant difference?
- What dosage was optimum? Does increasing dose increase effectiveness enough to justify extra cost?
- Was the cost of production & distribution low enough?
- What are the ethical issues surrounding the use of vaccines and monoclonal antibodies?
How do antibodies lead to the destruction of pathogens?
Antibodies bind to complimentary antigens on the surface of pathogens . Each antibody can bind to 2 pathogens at a time, causing agglutination. This allows the antibodies to attract phagocytes, which destroy the pathogens via phagocytosis.
Describe phagocytosis of pathogens
- Phagocyte is attracted to chemicals made by pathogen or recognises it’s foreign antigens on cell surface membrane.
- Phagocyte engulfs pathogen by endocytosis, surrounding it with its cell membrane.
- Pathogen contained in phagosome within the cytoplasm of the phagocyte.
- Lysosome fuses with phagosome to produce a phagolysosome and releases lysozymes.
- Lysozymes hydrolyse the pathogen and the products are absorbed into the phagosome if they are soluble, but are expelled from the cell if they are insoluble.
How can monoclonal antibodies be used in medical diagnosis?
Monoclonal antibodies have a specific tertiary structure and therefore their antigen binding site is complementary to the receptor of the antigen associated with diagnosis. Fluorescent markers can be attached to the monoclonal antibody, and if the antibody binds to the receptor of the specific antigen, it will form an antigen-antibody complex which will be visible so that scientists can diagnose diseases by identifying which antigen is present.
What is an antigen?
A foreign protein which stimulates an immune response, leading to the production of a complimentary antibody.
What are antibodies?
Antibodies are quaternary structure proteins and they consist of 4 polypeptide chains. They are secreted by B-Plasma cells in response to specific antigen. They are complimentary to their specific antigen, and when bind to it, they form an antigen-antibody complex.
What is the purpose of a control well in the ELISA test?
So that you can compare it to the test well to ensure that only the enzyme caused the colour change and that all unbound antibodies had been washed away.
Describe the response of T lymphocytes to a foreign antigen (the cellular response).
T-Lymphocytes recognise antigens on the surface of antigen presenting cells. Specific T-Helper cells with complimentary receptors on their cell surface bind to the antigen on the antigen-presenting cell, causing the T-Helper cells to divide rapidly by mitosis, which then stimulate the production of Cytotoxic T Cells (which produce chemicals such as perforin to kill infected cells and pathogens), Specific B Cells (which stimulate the humoral response, including the production of antibodies) and Phagocytes (which engulf pathogens by phagocytosis).
What is the non-specific immune response?
Phagocytosis
Explain the effect of antigen variability on disease and disease prevention.
The tertiary structure of the antigens on the surface of pathogens changes due to a mutation, causing a change in shape. Therefore, the B-memory cells can no longer bind to the antigen when exposed to the antigen, and the specific antibodies are no longer complimentary so can not bind to the antigen. Therefore, there is no more immunity.
What are the specific immune responses?
Cellular and humoral response.
Why are antibiotics ineffective against viruses?
Viruses do not have structures and processes that antibiotics inhibit. Viruses do not have metabolic processes and they do not have bacterial enzymes or a murein cell wall.
Describe the response of B lymphocytes to a foreign antigen (the humoral response)
B Lymphocytes can recognise free antigens. When they come across a foreign antigen, specific B-Lymphocytes with complimentary receptors bind to the antigens, and is stimulated by T-Helper cells to divide rapidly by mitosis. Some of these clones differentiate into B-Plasma cells, which secrete large amounts of antibodies, which are specific to the foreign antigen. Others differentiate into B-Memory cells, which remain in the blood until the secondary immune response.
Explain the use of antibodies in the ELISA test to detect antigens.
- Attach sample with potential antigens to well
- Add complementary monoclonal antibodies with enzymes attached. They will bind to antigens if present.
- Wash well to remove unbound antibodies (to prevent false positive)
- Add substrate so that the enzymes create products that cause a colour change (positive result)
What are the differences between the primary and secondary immune response?
The primary response refers to the immune response which occurs upon the first exposure to an antigen. Antibodies are produced slowly and at a lower concentration as it takes time for specific B-Plasma cells to be stimulated to produce the specific antibodies. Memory cells are produced in the primary response. The secondary response refers to the immune response that occurs upon the second exposure to an antigen. In the secondary response, antibodies are produced faster and at a higher concentration. This is because B memory cells are present in the blood, and they rapidly undergo mitosis in order to rapidly produce specific antibodies.
How do vaccines provide protection to individuals against disease?
- Specific B lymphocyte with complementary receptor binds to antigen
- Specific T helper cell binds to antigen-presenting cell and stimulates B cell
- B lymphocyte divides by mitosis to form clones
- Some differentiate into B plasma cells which release antibodies
- Some differentiate into B memory cells
- On secondary exposure to antigen, B memory cells are already present, so they can rapidly divide by mitosis to produce B plasma cells
- These release antibodies faster and at a higher concentration
How are cells identified by the immune system?
Each cell has specific antigen on it’s cell surface. These antigens are proteins and have a specific tertiary structure, which help the immune system to recognise them as self or foreign.
Explain the use of antibodies in the ELISA test to detect antibodies.
- Attach antigens to well that are complimentary to the antibody you are testing for.
- Add sample with potential antibodies, wash to remove unbound antibodies.
- Add complementary monoclonal antibodies
with enzymes attached, which will bind to antibodies if
present, - Wash well to remove unbound antibodies.
- Add substrate so that enzymes create products that
cause a colour change (positive result).
