Biology Chapter 5 (CGP) Flashcards
What are antigens?
Molecules that can generate an immune response when detected by the body, usually found on the surface of cells
Why do some antigens generate an immune response?
The immune system identifies them as foreign
What is a phagocyte?
A type of white blood cell that carries out phagocytosis
Describe phagocytosis
- A phagocyte recognises the foreign antigens on a pathogen
- The cytoplasm of the phagocyte moves round the pathogen, engulfing it
- The pathogen is now contained in a phagocytic vacuole in the cytoplasm of the phagocyte
- A lysosome fuses with the phagocytic vacuole. The lysozymes break down the pathogen
- The phagocyte then presents the pathogen’s antigens on its surface to activate other immune system cells. The phagocyte acts as an antigen-presenting cell
What are T-cells?
A type of white blood cell that have receptor proteins on their surface that bind to complementary antigens presented to it by phagocytes. This activates the T-cell
What is the function of helper T-cells?
To release chemical signals that activate and stimulate phagocytes. They also activate B-cells
What is the function of cytotoxic T-cells?
To kill abnormal and foreign cells
What are B-cells?
A type of white blood cell that are covered in antibodies. Each B-cell has a differently shaped antibody on its membrane, so different ones bind to different shaped antigens
What are antibodies?
Proteins that bind to antigens to form an antigen-antibody complex
What is clonal selection?
A scientific theory in immunology that explains the functions of cells (lymphocytes) of the immune system in response to specific antigens invading the body.
What do activated B-cells divide into?
Plasma cells
What are monoclonal antibodies?
Antibodies specific to the antigen, which bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes
What two regions do antibodies have?
Variable and constant region
What is agglutination?
When pathogens become clumped together due to an antibody binding to two pathogens at the same time
What is a cellular response?
T-cells
Other immune system cells that they interact with
What is a humoral response?
B-cells
Clonal selection
The production of monoclonal antibodies
What is the primary response?
When an antigen enters the body for the first time.
Slow
Not many B-cells that can make enough of the right antibody needed to bind to it
Symptoms shown in person
Memory cells produced
What is the secondary response?
Quicker Stronger Clonal selection is faster Memory B-cells are activated Symptoms often not shown
What is active immunity?
A type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen
What is passive immunity?
A type of immunity you get from being given antibodies made by a different organism
What is natural active immunity?
Becoming immune after catching a disease
What is artificial active immunity?
Becoming immune after being vaccinated
What is natural passive immunity?
When a baby becomes immune due to the antibodies it receives from its mother, through the placenta and in breast milk
What is artificial passive immunity?
Becoming immune after being injected with antibodies from someone else (e.g blood transfusion)
What is herd immunity?
When a person is less likely to catch a disease because there are many people who are vaccinated for it
Why are booster vaccines given?
To make sure that the memory cells are produced
What are ethical issues surrounding the use of vaccines?
- Animal testing
- Risky
- Side effects
- Decisions about who should receive it if an epidemic of a new disease occurs
What is antigenic variation?
When pathogens change their surface antigens
What is the ELISA test?
A test which allows you to see if a patient has any antibodies to a certain antigen or any antigen to a certain antibody. Used for medical diagnosis for pathogenic infections etc.
In an ELISA test, an antibody is used which has an enzyme attached to it. This enzyme can react with a substrate to produce a coloured product. This means the antigen or antibody of interest is present.
What is direct ELISA?
Uses a single antibody that is complementary to the antigen you’re testing for
Why is the well washed out in direct ELISA?
To remove any unbound antibody
What is indirect ELISA?
Uses two different antibodies
e.g HIV antigen bound to bottom of well in well plate. Sample of patient’s blood plasma, which might contain several different antibodies, is added to the well. If there are any HIV-specific antibodies in the plasma these will bind to the HIV antigen stuck to the bottom of the well. The well is then washed out to remove any unbound antibodies. A second antibody, that has a specific enzyme attached to it, is added to the well. This secondary antibody can bind to the HIV-specific antibody. The well is washed out again to remove any unbound secondary antibody. If there’s no primary antibody in the sample, all of the secondary antibody will be washed away because there will be nothing for it to bind to. A solution is added to the well. This solution contains a substrate, which is able to react with the enzyme attached to the secondary antibody and produce a coloured product. If the solution changes colour, it indicates that the patient has HIV-specific antibodies in their blood and is infected with HIV.
What are the ethical issues surrounding the use of monoclonal antibodies?
Animal right issues
What is HIV?
A virus that affects the human immune system, which eventually leads to AIDS
What is AIDS?
A condition where the immune system deteriorates and eventually fails, making someone with AIDS more vulnerable to other infections
How does HIV cause the symptoms of AIDS?
It infects and eventually kills helper T-cells, which act as the host cells for the virus. Without them, the immune system is unable to mount an effective response to infections because other immune system cells don’t behave like they should
When does HIV develop into AIDS?
When the helper T-cell number in their body reaches a critically low level
What is the latency period?
HIV replication drops to a lower level and the infected person won’t experience any symptoms.
What is the structure of HIV?
RNA Reverse transcriptase Capsid Envelope Attachment protein
Describe HIV replication
- The attachment protein attaches to a receptor molecule on the cell membrane of the host helper T-cell
- The capsid is released into the cell, where it uncoats and releases the genetic material (RNA) into the cell’s cytoplasm
- Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template
- From this, double-stranded DNA is made and inserted into the human DNA
- Host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA
- The viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells
Why are antibiotics ineffective against viruses?
Because viruses don’t have their own enzymes and ribosomes. Instead they use the ones in the host’s cells. Antibiotics don’t target human processes
How can HIV infection spread be reduced?
Protected sex
Take antiviral drugs during pregnancy if the mother has HIV
