2.4 Immunity Flashcards
What are the non-self cells?
Cells from transplants, abnormal (cancer) cells, and cells infected by a virus.
What type of cell are cells from transplants, abnormal (cancer) cells, and cells infected by a virus?
Non-self cells.
Define an antigen.
Foreign protein, which stimulates an immune response.
Describe and explain the process of phagocytosis.
- Phagocyte attracted to pathogen as it recognises foreign antigen
- Phagocyte engulfs pathogen by endocytosis, and encloses it into a phagosome
- Phagosome fuses with lysosome
- Lysosome releases enzymes which hydrolyse pathogen
- Antigens displayed on cell-surface membrane
How is a phagocyte attracted to a pathogen?
It recognises foreign antigen.
In what process does a phagocyte engulf a pathogen?
Endocytosis.
What fuses with each other during phagocytosis?
Phagosome fuses with lysosome.
What type of response is phagocytosis?
Non-specific immune response.
What are the two types of phagocytes?
Neutrophils and monocytes, which mature to macrophages.
What is the longevity of neutrophils?
Short-lived.
What is the longevity of monocytes?
Mature to macrophages, which are longer-lived.
Describe the cellular immune response.
T cell receptor specific for single antigen, Th cell with complementary antigen binds to antigen presenting cell, causes activation of Th cells to rapidly divide by mitosis, producing clones.
What can clones of Th cells do?
Become T memory cells, stimulate the humoral response, stimulate cytotoxic T cells.
How do cytotoxic T cells result in the death of other cells?
Produce the protein perforin, which makes holes in the cell-surface membrane.
Describe the humoral immune response.
Antigen binds to surface receptor on B cell, B cell engulfs by endocytosis and presents antigens on surface, T helper cell with complementary receptor binds to antigens, stimulates B cell to rapidly divide by mitosis, activated B cell can differentiate into B memory cells or plasma cells.
What can activated B cells differentiate into?
B Memory Cells and Plasma Cells.
What is the longevity of B Memory cells?
Long-lived.
What is the longevity of plasma cells?
Short-lived.
What is the purpose of B Memory Cells?
Can rapidly divide into plasma cells if the same antigen is encountered.
What is the purpose of plasma cells?
Produce antibodies.
What are antibodies produced by?
Plasma cells.
When does agglutination occur?
When an antigen and antibody bind with each other, forming an antigen-antibody complex.
What is the result of an antigen and antibody binding with each other?
Agglutination.
What is the purpose of agglutination?
Attracts phagocytes to increase the rate of phagocytosis.
Define an antibody.
Protein secreted by plasma cells which are specific to an antigen.
When does a primary immune response occur?
First time after an individual encounters a pathogen.
When does a secondary immune response occur?
Subsequent times after an individual encounters a pathogen (re-exposure).
Why is primary immune response slower than secondary immune response?
Fewer T and B cells in circulation.
What is the result of primary immune response that is not the result of secondary immune response?
Production of memory cells.
What is a key sentence regarding the secondary immune response?
Secondary immune response occurs quicker, and a higher concentration of antibodies are produced.
What is the final result of phagocytosis?
Pathogen antigens displayed on cell-surface membrane.
Describe how vaccination produces antibodies.
Vaccine contains antigen from pathogen, antigen binds to receptor on B cell, B cell engulfs by endocytosis and presents antigens on surface, T helper cell with complementary receptor binds to antigens, stimulates B cell to rapidly divide by mitosis, B cells differentiate into memory cells and plasma cells, plasma cells produce antibodies.
Active vs passive immunity: Memory cells.
Active involves memory cells; passive doesn’t involve memory cells.
Active vs passive immunity: Introduction of antibodies.
Active involves antibody production by plasma cells; passive involves antibody introduced from outside source.
Active vs passive immunity: Short or long-term, and why.
Active long-term as antibody is produced in response to antigen; passive short-term as antibody is broken down.
Active vs passive immunity: Time taken to work.
Active takes time to work; passive is fast-acting.
Why is herd immunity necessary?
Not all individuals can be vaccinated.
Explain the principle of herd immunity.
If a sufficient proportion of the population is vaccinated, then pathogen cannot be transmitted to unvaccinated individuals, as pathogen is destroyed before it reaches vulnerable individuals.
Where is reverse transcriptase enzyme found within a molecule of HIV?
Matrix.
Where are the attachment proteins found on a molecule of HIV?
Lipid envelope.
Describe the process of HIV replicating.
Attachment proteins attach to receptors on helper T cell, nucleic acid/RNA enters cell, reverse transcriptase converts RNA to DNA, viral protein/capsid/enzymes produced, virus (particles) assembled and released (from cell).
What are the structural features of an HIV particle?
Core, capsid, lipid envelope, protein attachments.
What does the HIV core contain?
The genetic material and the enzyme reverse transcriptase.
Is the genetic material in viruses DNA or RNA?
RNA.
What cells does HIV affect?
T helper cells.
How does HIV enter the T helper cells?
Injects RNA.
How does HIV affect the immune system?
HIV destroys T helper cells, so fewer B cells are activated/stimulated, resulting in less antibodies produced.
Explain how HIV affects antibody production.
HIV destroys T helper cells, fewer B cells are activated/stimulated, resulting in less antibodies produced.
Define a monoclonal antibody.
Antibodies with the same tertiary structure, produced from cloned plasma cells.
Why can monoclonal antibodies be used to treat disease?
Binds to specific antigens.
What type of immunity does monoclonal antibodies use the principle of?
Passive immunity.
Describe the process of using an ELISA test.
Antigen from sample being tested is attached to well, first antibody with complementary tertiary structure binds, add second antibody with enzyme attached that binds to first antibody, substrate added, colour change due to enzyme.
What does the first line on an antibody test strip prevent?
False negatives.
Explain why antibodies are specific to one antigen.
Variable region has a specific primary structure, so binding site has a specific tertiary structure, complementary in shape to antigen, forming an antibody-antigen complex.
Define a pathogen.
A microorganism that causes an immune response, and bodily harm.
Give one example of using monoclonal antibodies in a medical treatment.
Bullet drugs.
Give two ways in which a pathogen may cause disease when it has entered the body.
- Damage cells 2. Produce toxins.
Why are tests using monoclonal antibodies specific?
- Monoclonal antibodies have the same order & sequence of amino acids. 2. They also have the same tertiary structure. 3. They are only complementary to one antigen.
Describe how a phagocyte destroys a pathogen present in the blood.
- Engulfs pathogen 2. Forms a vesicle (phagosome) and fuses with lysosome 3. Enzymes (lysozymes) hydrolyse the pathogens.
Give two types of cells, other than pathogens, that can stimulate an immune response.
- Cancer cells 2. Organ transplant cells.
When a vaccine is given to a person, how does it lead to the production of antibodies?
- Vaccine contains antigen from pathogen 2. Macrophage presents antigen on its surface 3. T cell with complementary receptor protein binds to antigen 4. T cell stimulates B cell 5. With complementary antibody on its surface 6. B cell secretes large amounts of antibody 7. B cell divides to form clone all secreting/producing same antibody.
What is an antigen?
A foreign protein present on the surface of cells which trigger an immune response.
What is an antibody?
A protein found in the blood that is produced by plasma cells which bind to antigens as part of an immune response.
Explain why a high mutation rate makes it difficult to develop a vaccine.
- Vaccine contains specific antigen 2. Mutation causes antigens to change (shape) 3. Antibodies can’t bind to antigen, so no antibody-antigen complexes formed.
Explain the role of B-lymphocytes and T-lymphocytes against virus infection.
- B lymphocytes recognise antigen 2. Produce plasma cells which make antibodies 3. Antibodies agglutinate virus 4. T lymphocytes helpers produce chemicals 5. Encourages phagocytes to engulf clumped virus 6. Killer T cells kill infected cells.
Use your knowledge of phagocytosis to describe how an ADC enters and kills the tumour cell.
- Cell engulfs the ADC 2. Lysosomes fuse with vesicle (phagosome) containing ADC 3. Lysozymes digest (hydrolyse) the ADC to release the drug.
Explain how determining the genome of the viruses could allow scientists to develop a vaccine.
- Could identify proteins 2. Identify potential antigens (to be used in the vaccine).
Describe the structure of the human immunodeficiency virus (HIV).
- RNA = genetic material 2. Reverse transcriptase 3. Protein capsid 4. Lipid envelope 5. Attachment proteins.
A high mutation rate makes it difficult to develop a vaccine. Explain why (3)
- vaccine contains specific antigen
- mutation causes antigens to change (shape)
- antibodies can’t bind to antigen, so no antibody-antigen complexes formed
Describe and explain the role of antibodies in stimulating phagocytosis. (2)
- Bind to antigen
- Antibodies cause agglutination
Describe how a phagocyte destroys a pathogen present in the blood. (3)
- engulfs pathogen
- forms a vesicle (phagosome) and fuses with lysosome
- enzymes (lysozymes) hydrolyse the pathogens
Describe how phagocytosis of a virus leads to presentation of its antigens. (3)
- Phagosome vesicle fuses with lysosome;
- Virus destroyed by lysozymes
- Antigen are displayed on the cell membrane
Describe how the human immunodeficiency virus (HIV) is replicated once inside helper T cells (TH cells). (4)
- RNA converted into DNA using reverse transcriptase
- DNA inserted into TH cells DNA
- DNA transcribed into (HIV m)RNA
- HIV mRNA translated into HIV/viral proteins
Describe the role of antibodies in producing a positive result in an ELISA test. (4)
- first antibody binds - complimentary to antigen
- second antibody with enzyme attached is added
- second antibody attaches to antigen
- substrate added and colour change
Determining the genome of the viruses could allow scientists to develop a vaccine.
Explain how. (2)
- could identify proteins
- identify potential antigens (to be used in the vaccine)
During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom.
Use your knowledge of the humoral immune response to explain this vaccination programme (3)
- B cells specific to the venom reproduce by mitosis
- B cells produce plasma cells & memory cells
- The second dose produces antibodies in higher concentration and quicker.
Explain how a blood transfusion from a patient recently recovered from Ebola may be an effective treatment (3)
- Lots of antibodies (against Ebola) in recovered patient
- plasma contains antibodies
- antibodies will bind with ebola antigen
- in recipient the virus is destroyed
Explain how HIV affects the production of antibodies when AIDS develops in a person. (3)
- less antibody produced
- because HIV destroys helper T cells
- so few B cells activated -> less differentiate into plasma B cells
Explain how the treatment with antivenom works and why it is essential to use passive immunity, rather than active immunity. (2)
- antivenom bind to the toxin/venom and cause its destruction
- active immunity would be too slow
Explain the increase in specific plasma cells and antibody in people infected with the Ebola virus. (2)
- antigen on ebola binds to B cell
- Binding causes cloning of B cell
- plasma cells release antibodies
Explain the role of B-lymphocytes and T-lymphocytes against virus infection (6)
- B lymphocytes recognise antigen
- Produce plasma cells which make antibodies
- Antibodies agglutinate virus
- T lymphocytes helpers produce chemicals
- Encourages phagocytes to engulf clumped virus
- Killer T cells kill infected cells
give 2 types of cells, other than pathogens, that can stimulate an immune response (2)
- cancer cells
- organ transplant cells
Give one example of using monoclonal antibodies in a medical treatment. (1)
Bullet drugs
Give two ways in which a pathogen may cause disease when it has entered the body. (2)
- damage cells
- produce toxins
In the UK, children are vaccinated against this disease.
Describe how vaccination can lead to protection against bacterial meningitis. (6)
- Antigen bacteria binds to surface receptor on a specific B cell.
- B cell divides by mitosis
- Division stimulated by T cells
- B cells / plasma cells release antibodies
- B cells become memory cells
- Memory cells produce plasma / antibodies faster
People who do not have the specific receptor protein in their cell-surface membranes may be infected with the Ebola virus but do not develop the disease
Explain why they do not develop the disease. (2)
- virus can’t bind to receptor
- so can’t be replicated
- so doesn’t damage cells/tissues
Previously, the viruses infected only one species of frog.
(a) Suggest and explain how the viruses became able to infect other species of frog. (2)
- Mutation in the viral DNA
- Altered the tertiary structure of the viral attachment protein
Some of the antigens found on the surface of tumour cells are also found on the surface of healthy human cells.
Use this information to explain why treatment with an ADC often causes side effects. (2)
- ADC will bind to healthy cells
- cause death/damage of healthy cells
Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why. (3)
- monoclonal antibodies have the same order & sequence of amino acids
- and also the same tertiary structure
- so they are only complimentary to one antigen
This test only detects the presence of HIV antibodies. Give two reasons why it cannot be used to find out if a person has AIDS. (2)
to diagnose aids, need to look for:
1. AIDS-related symptoms
2. number of helper T cells
Use your knowledge of phagocytosis to describe how an ADC enters and kills the tumour cell. (3)
- cell engulfs the ADC
- lysosomes fuse with vesicle (phagosome) containing ADC
- Lysozymes digest (hydrolyse) the ADC to release the drug
