2C: Cells and the Immune System Flashcards
What are antigens?
molecules that can generate an immune response when detected in the body
What can antigens allow the immune system to identify?
Pathogens
Abnormal Body Cells
Toxins
Cells from another individual of the same species
What are pathogens?
organisms that cause disease
What are the 4 types of pathogen?
Bacteria, Fungi, Virus, Protist
What are toxins?
Posinous molecules released by bacteria
Describe Phagocytosis
- phagocyte regognises foreign antigens on a pathogen
- they cytoplasm of the phagocyte moves round the pathogen, engulfing it inot a phagosome/phagocytic vacuole
- a lysosome fuses with the phagosome ans releases lysozymes to break down the pathogen
- the phagocyte presents the pathogen’s antigens on its cell surface membrane
What is a phagocyte?
a type of white blood cell that carries out phagocytosis
What is a T-cell?
a type of white blood cell which has receptor proteins on its surface that bind to complementory antigens presented to it by phagocytes
What are the 2 types of T-Cell?
Helper and Cytotoxic
What to helper T-Cells do?
release chemical signals that activate phagocytes and cytotoxic T-Cells
What do cytotoxic T-Cells do?
kill abnormal and foreign cells by producing porferin and granzymes
What are B-Cells?
a type of white blood cell that present or secrete antibodies
What can a B-Cell turn into?
Memory B-Cell of Plasma Cell
Describe the process of immune response
on poster
What is the Humoral response ?
B-Cells, clonal selection and the production of monoclonal antibodies
What is agglutination?
when an antibody has 2 binding sites so can bind to 2 pathogens at a time meaning the pathogens are clumped together
What is clonal selection?
The process of matching the antigens on an antigen presenting cells with the antigen receptors on B and T lymphocytes
What is the Cellular response?
T-Cells and other immune system cells that they interact with eg. phagocytes
What is the primary immune response?
When an antigen enters the body for the first time, it generates a primary immune response
It is slow and produces memory cells
What is the secondary immune reponse?
If the same antigen enters the body again, the immune system will produce a secondary response
This is much faster as the body has the memory cells
What is Active Immunity?
The type of immunity you get when your immmune system makes its own antibodies after being stimulated by an antigen
What are the 2 types of active immunity?
Natural: when the body becomes immune after catching a disease
Artificial: when the body becomes immune after its been given a vaccination exposing it to a harmless dose of antigen
What is Passive Immunity?
The type of immunity you get from being given antibodes made by a different organism
What are the 2 types of passive immunity?
Natural: when the baby becomes immune due to the antibodies it recieves from its mother
Artificial: when you become immune after being injected with antibodies from someone else
Compare Active and Passive Immunity
Active Immunity:
- requires exposure to antigen
- takes a while for protection to develop
- memory cells are produced
- long-term protection
Passive Immuity:
- doesn’t require exposure to antigen
- immediate protection
- memory cells aren’t produced
- short-term protection
What is herd immunity?
When the use of vaccines reduces the occurance of a disease
What are the ethical issues with using vaccines?
- tested on animals
- risk of side effects
- in an epidemic, there is a rush for vaccines, so hard to choose who will get them first
What is antigenic variation?
When the antigens on the surface of pathogens change
What are monoclonal antibodies?
Antibodies produced from a single group of genetically identical B-Cells (plasma cells)
How are monoclonal antibodies made?
fusing spleen cells from an immunised mouse with human or mouse myeloma (tumor) cells to produce hybrid cells. then cloning them to produce desired antibody
What are monoclonal atibodies used for?
Anti-cancer drugs targeted to cancer cells
Pregnancy Tests
Describe how Monoclonal antibodies are used in pregnancy tests
Pregnancy tests detect the hormone human chrionic gonadotropin (hCG) found in urine
- the application area contains antibodies that are complementory to the hCG protein, bound to a coloured blue bead
- when urine is applied to the application area, any hCG will bind to the antibody on the beads, forming an antigen-antibody complex
- the urine moves up the stick to the test strip, carrying any beads with it
- the test strip contains antibodies to hCG that are immobilised
- if there is hCG present the test strip turns blue because the immobilised antibody binds to any hCG, concentrating the hCG-antibody complex with the blue beads attached
- if no hCG is present the beads will pass through the test area without binding and won’t turn blue
What is an ELISA Test?
An Enzyme-linked Immunosorbent Assay that allows you to see if a patient has any antibodies to a certain antigen or an antigen to a certain antibody
Describe a Direct ELISA Test
- antigens from a patient sample are bound to the inside of a well in a well plate
- a detection antibody (with an attached enzyme) that is complementary to the antigen of interest is added
- if the antigen of interest is present in the patient sample, it will be immobilised on the inside surface of the well and the detection antibody will bind to it
- well is washed out to remove unbound antibodies and a substrate solution is added
- if the detection antibody is present, the enzyme reacts with the substrate to give a colour change, this is a positive result
Describe an Indirect ELISA Test
- HIV antigen is bound to the bottom of a well in a well plate
- a sample of the patients blood plasma is added to the well. if there are any HIV-Specific antibodies in the plasma, they will bind to HIV Antigens
- wash out to remove unbound antibodies
- a secondary antibody, that has a specific enzyme attached to it, is added to the well. this antibody can bind to the HIV specific antibody
- well is washed out to remove unbound antibodies
- a solution containing a substrate which is able to react with the enzyme is added
7 if the solution changes colour, HIV antibodies are in the plasma
What is HIV?
Human Immunodeficiency Virus is a virus that affects the human immune system
What is AIDS?
Acquired Immune Deficiency Syndrome is a condition where the immune system deteriorates and eventually fails
What does the HIV Virus do?
It kills helper T-Cells, which act as a host for the virus
What are the Stages and Symptoms of HIV?
In the initial infection period when HIV rapidly replicates and the infected person experiences severe flu-like symptoms
Latency Period- after initial infection, the infected person won’t experience any symptoms, this can last years
What are the symptoms of AIDS?
a series of infections, increasing in severity
When is a HIV infected person classes as having AIDS?
when symptoms of their failing immune system start to appear or helper T-Cells drop below a certain level
Describe the structure of HIV
A capsid containing RNA and reverse transcriptase surrounded by an envelope with attachment proteins
Describe HIV Replication
- 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 assembles into new viruses, which bud from the cell and go on to infect other cells
What are antibiotics?
medications that kill bacteria
What are antivirals?
drugs designed to target the few virus-specific enzymes that exist
How is HIV Infection controlled?
drugs can be used to slow progression of HIV
best way is to prevent by:
- protected sex
- new needles
- taking antiviral drugs during pregnancy
