11. Immunity Flashcards
Explain how macrophages function to protect the lungs from becoming infected. [4m]
- macrophages recognise non-self antigens on pathogens
- receptor on macrophage binds to antigen on pathogen
or pathogen adheres to CSM - infolding of macrophage CSM around / engulf pathogen
- vesicle forms
- lysosomes that contain hydrolytic enzymes destroy pathogen
Explain why polysaccharides would not be suitable for making antibody molecules. [2m]
- polysaccharides are made from a small number of different sugars
- unlike proteins which are made from 20 amino acids
- polysaccharides would not give the huge no. of different molecular shapes in the variable region of antibodies as is achieved with proteins
Suggest why the results for a single sample of blood taken from a patient on admission to hospital should be interpreted with care. [3m]
- the patient may never have had such a blood test before
- there is no way to know if the no. of blood cells have changed as a result of infection
- wide ranges of results are normal
- there are a variety of causes for high or low numbers of blood cells
Explain why myasthenia gravis (MG) is known as an autoimmune disease. [3m]
- failure to distinguish between self and non-self
- specific B-lymphocytes are not destroyed during development
- antibodies are produced against ACh receptor on muscle cells
- antibodies bind to receptor
- thus acetylcholine cannot bind to receptor
- nerve impulses are not transmitted across neuromuscular junction
- causing muscle fatigue
Suggest why MG is a long-term condition. [2m]
- immune response occurs all the time
- defective B-lymphocytes still being produced
- plasma cells continue to release antibodies against receptors
- memory cells present
- no cure
A monoclonal antibody is labelled with the radioactive isotope indium-111, which emits low-energy gamma rays that can pass through soft tissues of the body. The half life of indium-111 is 2.8 days
Suggest why indium-111 is a suitable radioactive label for this diagnostic antibody. [3m]
- emits gamma-rays, which pass though soft tissues and so can be diagnosed from outside the body
- weak gamma-rays, reducing chance of mutation
- short half-life, so no continuing source of gamma-rays
- indium has no biological role
Monoclonal antibody
- identical antibodies produced by cloning
- variable regions/antigen-binding sites are all identical; antibodies are specific to 1 antigen
Explain how vaccination can control infectious diseases. [3m]
- vaccination gives active IMMUNITY
- clonal selection/expansion of specific B-lymphocytes occurs, involving formation of antibodies and memory cells
- presence of antigen gives faster, secondary immune response
- effect of vaccination is long-lived as memory cells remain in circulation for long time
- herd effect produced when >90% people vaccinated, so non-vaccinated people are protected
- stop transmission cycle
Explain why countries that have established vaccination programmes still have cases of measles. [2m]
- measles introduced by people who caught the disease when abroad
- herd immunity needs to be >90%
- some people in these countries have not vaccinated
- some people do not respond to vaccine (weak immune system/malnutrition)
- some people do not receive boosters
- vaccine is not thermostable
Some strains of V. cholerae are antibiotic resistant.
Explain why medical practitioners prefer to treat cholera with a single dose of antibiotic, rather than a multiple dose of the same antibiotic. [2m]
- single dose is easier to ensure patient has taken complete dose; course may not be completed for multiple dose
- if all bac. are susceptible and treatment completed, all bac. killed by single dose; if multiple dose given, treatment may not be completed so some susceptible bac. survive
- thus multiple dose increases chance of mutation
- if resistance already present, single stronger dose has greater chance of killing resistant bac.
Explain why the concentration of antibody (eventually) falls. [3m]
- no more antigen
- no more antibodies produced
- plasma cells are short-lived
- antibodies eventually broken down in liver
Outline the use of monoclonal antibodies in the treatment of disease. [2m]
- specific treatment
- bind to antigens on cell surface of diseased cells
- kill the cell by stimulating immune system
- attach radioactive substances/drug to kill diseased cells
- treat infectious diseases / bind to antigens on pathogens
6 advantages of using monoclonal antibodies in diagnosis of disease
- monoclonal antibodies used all have the same specificity
- detect only one antigen
- can distinguish between different pathogens
- can be labelled/tagged, eg. with fluorescent label
- can detect location of tissue expressing antigens / cancer cells / blood clots
- faster diagnosis
Immune response
The reaction of the body to the presence of a foreign antigen
Describe how mitosis is involved in an immune response. [3m]
- occurs in both primary & secondary immune response
- SPECIFIC B- and T-cells divide by mitosis
- clonal expansion producing clones
- mitosis in memory cells for rapid secondary response
