Flashcards
Chapter 5: Cell Recognition and then Immune System
Cards in this deck (82)
- 1What is a pathogen?Disease-causing micro-organism
- 2What is immunity?The means by which the body protects itself from infection
- 3Examples of defence mechanisms- Skin
- Hairs
- Mucus
- Lymphocytes - 4What is non-specific immunity?- Immediate response
- Same for all pathogens; does not distinguish between them
- Defences: physical barriers, phagocytosis - 5What is specific immunity?- Slower response
- Specific to each pathogen
- Long-lasting immunity
- Defences: cell-mediated responses (T cells), humoral responses (B cells) - 6What allows lymphocytes to distinguish between self and non-self materials?Specific molecules on the surface of each cell; most importantly proteins as there is a large variety and they have very specific tertiary structures
- 7What non-self materials do proteins allow the immune system to identify?- Pathogens
- Non-self materials (e.g. cells from other organisms of same species, such as an organ transport)
- Toxins
- Abnormal body cells (e.g. cancer cells) - 8What are often used for organ transplant patients to prevent an immune response?Immunosuppressant jobs
- 9Why are specific lymphocytes not produced?Around 10 million already exist in the body; highly likely that one will be complementary to a pathogen antigen
- 10What is clonal selection?Division of lymphocytes to a level where it will be effective at destroying the pathogen; because of this there is a time lag between exposure to the pathogen and defence mechanisms controlling it
- 11How do lymphocytes recognise self-materials in a fetus?Lymphocytes constantly colliding with other cells - almost exclusively self materials as it is protected from infection by the mother/placenta
Some lymphocytes will have receptors which are complementary to self-antigens - these either die or are suppressed
Remaining lymphocytes are those that might complement non-self antigens; these remain in the blood - 12How do lymphocytes recognise self-materials in adults?Lymphocytes produced in the bone marrow initially only encounter self-antigens
Those that are complementary undergo apoptosis (programmed cell death) so no clones are made - 13What are phagocytes and what do they do?White blood cells which engulf and destroy pathogens
- 14Describe the process of phagocytosis?1. Phagocyte is attracted to chemical products produced by pathogens/dead cells etc, so it moves towards the pathogen along a concentration gradient (chemotaxis)
2. Phagocytes have multiple receptors which recognise and attach to chemicals on surface of pathogen
3. Engulfs pathogen to form a vesicle called a phagosome
4. Lysosomes move towards the vesicle and fuse with it
5. Lysozymes released from lysosomes destroy ingested bacteria by hydrolysis of the cell wall
6. Soluble products from breakdown of pathogen are absorbed into cytoplasm of phagocyte - 15What is an antigen?Any part of an organism or substance that is recognised as non-self by immune system and stimulates an immune response; triggers production of an antibody
- 16Comparison of B cells and T cells- B cells mature in bone marrow/T cells mature in thymus
- B cells involved in humoral immunity/T cells involved in cell-mediated immunity
- B cells work to kill non-self materials outside of cells/T cells work to kill non-self materials inside body cells
- B cells produce antibodies - 17What is cell-mediated immunity?Immunity regarding body cells where lymphocytes respond to an organisms own cell that have been infected by non-self material; will also respond to cells from individuals of the same species as they are genetically different so have different antigens
- 18How can T lymphocytes distinguish between invaded cells and normal cells?- Phagocytes which have engulfed and hydrolysed a pathogen will present some of a pathogens antigens on their own surface
- Body cells invaded by a virus present viral antigens on surface as a distress signal
- Transplanted cells from individuals of the same species have different antigens
- Cancerous cells present different antigens than normal cells - 19What is an antigen-presenting cell?A cell which can display foreign antigens on its own cell surface membrane
- 20How many antigens will a T cell receptor respond to?Only one - very specific
- 21Describe the process of the cell-mediated response1. Pathogens invade body cells or are engulfed by pathogens; antigens are presented on the surface of these cells
2. Receptors on a specific T helper cell are complementary to these antigens
3. Binding to these antigens stimulates T cells to divide rapidly by mitosis to form a clone of genetically identical cells - 22What 4 things can cloned T cells then do?1. Develop into memory cells to enable a more rapid response to future infections by the same pathogen
2. Stimulate phagocytes to engulf pathogens by phagocytosis
3. Stimulate B cells to divide and secrete their antibody
4. Activate cytotoxic T cells - 23How do cytotoxic T cells kill infected cells?`- Produce a protein calls perforin that makes holes in the cell surface membrane
- Cell membrane becomes freely permeable to all substances so the cell dies - 24What are T cells most effective against and why?Viruses because they replicate inside living host cells; killing the cell prevents replication of virus and infection of more cells
- 25What is humoral immunity?Immunity involving antibodies which are soluble in blood and tissue fluid
- 26Describe the process of humoral immunity1. There will be a B cell that produces a complementary antibody to the non-self antigen, and it binds to it
2. Antigen enters B cell by endocytosis and is processed and presented on its surface
3. T helper cells bind to these antigens, which stimulates the B cell to divide by mitosis to form a clone of identical B cells which all secrete a same specific antibody
4. Antibody attaches to antigens on the pathogen and destroys it - 27What are the 2 types of cell that a B cell clone can develop into?Plasma cell
Memory cell - 28What does a plasma cell do?- Secretes antibodies into blood plasma
- Short life span
- May make around 2000 antibodies per second
- Primary immune response - immediate response against infection - 29What does a memory cell do?- Does not produce antibodies; circulates in blood and tissue fluid
- Longer life span than plasma cells (decades)
- When the pathogen is encountered at a later time, they divide and develop into either plasma cells or more memory cells; this repeats to provide long-term immunity
- Secondary immune response; increased number of antibodies secreted at a faster rate than in the primary immune response - 30Why might more than one B cell need to produce a clone?A typical pathogen has many different proteins on surface which all act as antigens, and some also produce toxins which each act as an antigen
- 31What are antibodies?Proteins with specific binding sites synthesised by B cells; reacts with an antigen by binding to it
- 32What is the structure of an antibody?- Four polypeptide chains: chains of one pair are long (heavy chains) and chains of the other pair are shorter (light chains)
- Two identical binding sites; different on different antibodies so known as the variable region; each consists of a specific tertiary structure
- Remainder of the antibody is the constant region which binds to receptors such as on B cells - 33What is formed when a complementary antibody binds to an antigen?Antigen-antibody complex
- 34How do antibodies lead to the destruction of antigens?Do not directly destroy antigen
- Cause agglutination of bacterial cells; clumps of bacteria are formed which makes it easier for phagocytes to locate them
- Serve as markers that stimulate phagocytes to engulf the bacterial cells they are attached to - 35What about the structure of the antibody makes agglutination possible?Two binding sites with a hinged region
- 36What are monoclonal antibodies?Antibodies produced by a single clone of cells
- 37What are 3 uses of monoclonal antibodies?Medicinal diagnosis
Targeting medication to specific cell types
Pregnancy testing - 38What diseases/infections can monoclonal antibodies be used to diagnose?Influenza, hepatitis, chlamydia; provide much more rapid result than conventional methods of diagnosis
Also used to diagnose certain cancers - 39How can monoclonal antibodies be used to diagnose prostate cancer?- Men with prostate cancer often produce more of a protein called prostate specific antigen (PSA); higher levels in the blood
- Use of a monoclonal antibody which interacts with PSA makes it possible to obtain a measure of the level of PSA in a sample of blood
NB: this is not in itself diagnostic of prostate cancer but gives an early warning sign and need for more tests - 40How are monoclonal antibodies produced?1. An organism (such as a mouse) is exposed to a non-self material (e.g. cancer cells) against which an antibody is needed
2. B cells of the mouse will produce specific antibodies to the non-self antigens and these are extracted from the spleen
3. B cells are mixed with tumour/myeloma cells to enable them to divide outside the body
4. Detergent is added to the mixture to break down the cell membranes of both types of cell so that they fuse together to form hybridomas
5. Hybridomas are separated under a microscope; each single cell is cultured to form a clone and then each clone is tested to see if it produces the required antibodies
6. Any clone that produces the required antibodies are grown on a large scale and extracted from the growth medium - 41Describe direct monoclonal antibody therapy- Monoclonal antibodies that are specific to antigens on the cancer cells are produced
- Antibodies given to patient at attach themselves to receptors on cancer cells
- Attaching to surface blocks chemical signals which stimulate the uncontrolled growth - 42What is an example of a monoclonal antibody used to treat cancer?Herceptin; used to treat breast cancer
- 43What is the advantage of using direct monoclonal antibody therapy over other forms of therapy?They are non-toxic and highly specific, so lead to fewer side effects
- 44Describe indirect monoclonal antibody therapy?- Attaching a radioactive or cytotoxic drug to the monoclonal antibody
- When the antibody attaches to cancer cell receptors, it kills them - 45What is an advantage of using indirect monoclonal antibody therapy instead of only administering drugs?Can be used in smaller doses as they are targeted on specific sites - this is more cost-effective and reduces any side effects the drug might have
- 46What do pregnancy testing kits rely on?The placenta producing the human chorionic gonadatrophin (hCG) hormone, found in mother's urine
- 47Describe how a pregnancy test works- Monoclonal antibodies present on the strip of the test are linked to coloured particles
- If hCG is present in the urine, the antibodies bind to it
- hCG-antibody-colour complex is formed and this moves along the strip until trapped by a different antibody, creating a coloured line - 48What are some ethical issues associated with the use of monoclonal antibodies?Mice:
- Involves deliberately inducing cancer
- Creating transgenic animals (giving mice properties of a human to make the antibodies suitable for use in humans)
- Respiratory issues due to build up of fluid in the abdomen (ascites)
- FCA given to mice to enhance the immune system is painful when injected
- Pristane given as a priming agent causes inflammation
Humans:
- Testing new drugs presents concerns: lots of students taking part in drug trials to get money, is it fair to take advantage of people like this?; in March 2006, 6 healthy volunteers suffered multiple organ failure after a new monoclonal antibody led to over-stimulating immune system
- Expensive to produce; could funding go to finding other cures for diseases?
- Some deaths reported after used to treat multiple sclerosis
- Side effects: allergic reactions, flu-like symptoms, faintness, fatigue, breathlessness - 49Positive impacts of the use of monoclonal antibodies- Specific so can often diagnose diseases earlier than other methods of diagnosis; increases chances of a patient surviving and often less intense treatment is required (saves money on treatment for NHS; money can be spent elsewhere)
- Used to detect early pregnancies so mother can take precautions to ensure welfare of child
- Use in cancer treatment: less severe side effects than e.g. chemotherapy
- Can reduce effects of autoimmune diseases by binding to T cells
- Once a hybridoma has been made, easy to produce on a large scale - 50What are the 2 types of immunity?Passive immunity
Active immunity - 51What is passive immunity?Produced by introduction of antibodies from an outside source (no direct contact with the antibody is required)
Immunity is acquired immediately
Immunity does not last - 52Why does passive immunity not last?The individual is not producing the antibodies themselves so they are not replaced when they are broken down and no memory cells produced
- 53Give some examples of passive immunityAnti-venom given to victims of snake bites
Immunity acquired by fetus as antibodies pass from mother across the placenta - 54What is active immunity?Produced by stimulating production of antibodies by the individual's own immune system
Direct contact with the pathogen/antigens is required
Immunity takes time to develop
- Immunity is usually long-lasting
- 2 types - 55What are the 2 types of active immunity?Natural active immunity
Artificial active immunity - 56What is natural active immunity?When the individual becomes infected by the disease under normal circumstances so the body produces its own antibodies against it
- 57What is artificial active immunity?Forms the basis of vaccination; involves inducing an immune response without the person suffering the symptoms of the disease
- 58What is a vaccination?The introduction of the appropriate disease antigens into the body, either by injection or orally, in order to induce artificial active immunity
- 59What does a vaccination contain?One or more type of antigen from the pathogen
- 60What are 5 features of a successful vaccination programme?1. Suitable vaccine economically available in sufficient quantities
2. Few side effects, if any - unpleasant side effects might discourage people from having the vaccine
3. Way of producing, storing and transporting the vaccine - technologically advanced equipment, hygienic conditions, refrigerated transport
4. Means of administering the vaccine properly at the appropriate time - training sufficient number of staff
5. Must be possible to vaccinate the majority of a vulnerable population to produce herd immunity - 61When does herd immunity arise?When a sufficiently large proportion of the population has been vaccinated to make it difficult for the pathogen to spread in the population
- 62What idea is herd immunity based on?That pathogens are passed between people in close contact; if majority is immune, it is highly unlikely that an unprotected person will come into contact with an infected person
- 63Why is herd immunity important?It is never possible to immunise everybody in a large population - babies/young children, people with compromised immune systems
- 64What makes herd immunity the most effective?When the vaccination is carried out at one time; interrupts transmission of the pathogen
- 656 reasons why vaccination may not eliminate the disease1. Vaccine fails to induce immunity in certain people (e.g. those with defective immune systems)
2. People might develop disease immediately after vaccination before immunity levels are high enough to prevent it - harbour pathogen and reinfect others
3. Antigenic variability - pathogen may mutate frequently/antigens change so vaccine is ineffective as complementary antibodies are not produced; immunity is short-lived
4. Impossible to develop a vaccine effective against all varieties if there are many varieties of a pathogen
5. Some pathogens 'hide' from immune system - concealing themselves inside cells or living in places out of reach
6. People may have objections to vaccines for religious, ethical or medical reasons - 66Ethical issues surrounding the use of vaccines- Use of animals in production of vaccines
- Personal choice vs greater good of the public
- Informed consent: should consent be required, if so who should provide it? vs should they be compulsory?
- Accessibility: when vaccines are in short supply, who decides which groups of people they go to? How can vaccination be ensured in developing countries and low-income families?
- Is it acceptable to trail a new vaccine with unknown health risks in a country where the targeted disease is common, on the basis that the population has the most to gain if it proves successful?
- Should an expensive vaccine programme be continued if a disease is almost eradicated, even if this means less money for treatment of other diseases?
- Balancing side effects against the risk of developing a disease which might cause greater harm - 67What does HIV stand for?Human immunodeficiency virus
- 68What is the structure of HIV?- Lipid envelope on outside with attachment proteins embedded
- Capsid: protein layer enclosing two single strands of RNA and some enzymes, including reverse transcriptase - 69To what group of viruses does HIV belong and why?Retroviruses
Presence of reverse transcriptase - 70How is HIV replicated?1. Enters bloodstream and circulates around body
2. Attachment protein readily binds to CD4 protein
3. Capsid fuses with CSM, and RNA and enzymes enter the cell
4. Reverse transcriptase converts virus's RNA into DNA
5. Newly made DNA moves in nucleus via a nuclear pore and inserted into DNA of the cell
6. HIV DNA creates mRNA using cell's enzymes (e.g. RNA polymerase) - this will be used to make new viral proteins and RNA for new HIV
7. mRNA passes out of nucleus via nuclear pore and uses cell's protein synthesis mechanisms to make HIV components which form particles
8. Particles break away from cell with a piece of CSM which forms lipid envelope - 71What cells do HIV particles most often attach to?T helper cells
- 72Why can HIV recommence years after a person being infected?Often goes into dormancy
- 73What does AIDS stand for?Acquired immune deficiency syndrome
- 74How many T helper cells does an uninfected person normally have?800-1200 per mm3 of blood
- 75How many T helper cells might a person infected with HIV/AIDS have?As low as 200 per mm3 of blood
- 76How does HIV cause symptoms of AIDS?By killing or interfering with normal functioning of T helper cells
Without sufficient quantity of T helper cells, the immune system cannot stimulate B cells to produce antibodies, or cytotoxic T cells to kill infected cells; memory cells may also be killed
Body is unable to produce an adequate immune response so becomes susceptible to other infections and cancers - 77What are some common infections/issues developed by sufferers of AIDS?Infections of: lungs, intestines, brain, eyes
Weight loss
Diarrhoea - 78What is the cause of death of AIDS sufferers?Secondary diseases
- 79What is the ELISA test?Enzyme linked immunosorbent assay
Uses antibodies to detect presence and quantity of a protein in a sample
Used to detect HIV, TB, hepatitis
Extremely sensitive so can detect very small quantities - 80What is the procedure for the ELISA test?1. Apply sample to surface (e.g. slide) to which all antigens will attach
2. Wash several times to remove unattached antigens
3. Add antibody specific to antigen that needs to be detected and leave to bind to antigen
4. Wash to remove excess antibody
5. Add second antibody with enzyme attached that binds with first antibody
6. Add colourless substrate of enzyme that will change to a coloured product if enzyme acts on it
7. Amount of antigen present is relative to intensity of colour that develops - 81How do antibiotics prevent bacteria forming normal cell walls?- Water constantly enters bacterium by osmosis; peptidoglycan cell wall prevents bursting by preventing further entry
- Antibiotics (e.g. penicillin) inhibit certain enzymes needed for synthesis and assembly of peptide cross-linkages in the cell wall
- This makes cell wall weak and unable to withstand pressure from water - 82Why are antibiotics ineffective against viral diseases like AIDS?- Viruses rely on host cell to carry out metabolic activities as they don't have their own metabolic pathways; there is nothing for antibiotics to interrupt
- Viruses have viral protein coats rather than peptidoglycan cell walls so there are no sites where antibiotics can work
- Viruses are within an organism's own cells; antibiotics cannot reach them
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- A level Biology (AQA A level new spec content) Flashcards on Chapter 5: Cell Recognition and then Immune System, created by Amy Warrell on 06/05/2018.
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