A8 Immunology and HIV Flashcards
Describe Phagocytosis.
- Phagocyte recognises antigen and engulfs the pathogen
- A phagosome is formed which then fuses with a lysosome which contains hydrolytic enzymes
- This is called a Phagolysosome
- The pathogen is hydrolysed and the debris is released by exocytosis
- The antigen is presented on the cell surface membrane so the phagocyte becomes an APC ( Antigen Presenting Cell)
What two type of cells can lymphocytes be split into?
B and T cells
Name all B cell lymphocytes.
- B plasma cell
- B memory cell
Name all T cell lymphocytes.
- T Helper cell
- T killer cell
- (T memory cell)
Where do B cells mature?
Bone marrow
Where do T cells mature?
Thymus
What are the functions of the B memory cell?
- Can divide by mitosis
- Lives a long time and when activated they can differentiate into a plasma cell
What are the functions of a B plasma cell?
- Makes and secretes antibodies
- Can’t do mitosis
What is the function of the T helper cell?
- When activated it will divide by mitosis and differentiate into killer cells, more helper cells or memory cells.
- It activates other cells in the immune system and activated themselves by APC or pathogen
What is the definition of an immune response?
The immune response is a complex series of responses in the body to the entry of a foreign antigen; it involves the activity of phagocytes and lymphocytes.
What is the definition of a disease?
The malfunction of part or whole of the body with a characteristic set of symptoms
What is the definition of an antigen?
- Proteins or glycolipids on the surface of a cell/pathogen that can trigger an immune response
What are the four types of pathogens?
- Virus
- Bacteria
- Fungi
- Protist
Describe the steps in Humoral Response.
- The T helper cell has a complimentary specific receptor that binds to the presented antigen.
- This activates the cell causing mitosis
- The T helper cell activates the correct complimentary B cell, this is called clonal selection
- The B cells are activated and divide by mitosis which is called clonal expansion
- The clones can either become B memory cells or B plasma cells where antibodies are secreted and released
Describe the steps in Cell Mediated Response.
- Activation causes mitosis of the T helper cells and the clones that are made can become Cytotoxic T cells ( T killer cells). The infected host cell contains a presented pathogen’s antigen that the T killer cell binds to.
- This causes the T killer cell to release Perforin
- Perforin make holes in the cell membrane which causes the infected cell to lyse (burst)
What does an antibody contain in its structure?
- Antigen binding sites
- Heavy and light chains
- Variable region and constant region
- What holds the light and heavy chains together/ disulphide bonds
- Antigen binding site
What holds the polypeptides/ light and heavy chains together?
Disulphide bonds/bridges
What is active immunity?
When antibodies are produced by the persons’ B plasma cells
What is passive immunity?
When antibodies are injected or pass from the mother to the child
What is natural immunity
- Non man - made
What is Artificial immunity?
Man - made
Give an example of a natural and passive immunity.
Antibodies passed by breast milk across the placenta
Give an example of a natural and active immunity.
Infection
Give an example of an artificial and passive immunity.
Immunoglobulins ( antibodies injected via Ig therapy)
Give an example of an artificial and active immunity.
Vaccination
What is the definition of antigenic shift?
Larger changes to antigen structure that don’t compliment the previous memory cells and doesn’t trigger a secondary response.
What is the definition of antigenic drift?
Minor changes in antigen structure that can still trigger a secondary response - are still effected by the previously specific memory cells
Describe the steps in the Hybridoma method.
- Inject a mouse with antigen of interest
- This triggers an immune response
- B plasma cell produces antibodies that are complimentary to the antigen of interest
- The B plasma cell is hybridised ( fused ) with a myeloma cell as plasma cells cannot divide by mitosis but the myeloma cell divides rapidly
- This forms a Hybridoma cell which can divide by mitosis to produce lots of specific monoclonal antibodies
- The hybridoma cell secretes antibodies and divides by mitosis
- We then isolate the monoclonal antibodies
Draw a diagram of an antibody.
check notes
What does the ELISA test stand for?
Enzyme Linked Immunosorbent Assay
What does enzyme linked mean?
The monoclonal antibody has an enzyme attached to it
Describe the DIRECT ELISA test.
- Use a well with patient’s antigens in from the blood sample
- Add enzyme-linked antibodies
- The antigen for the disease that is being tested for is complimentary to the enzyme - linked antibody
- Wash out excess unbound antibodies and add substrate to the enzyme linked to the antibody
- For a positive sample the colour will change but for a negative sample it will remain the same ( no colour change )
Describe the INDIRECT ELISA test.
- Use a well with antigens of the disease that is being tested for
- Add the patient’s blood plasma
- The antibodies that are specific to the antigen of the disease that is being tested for, binds to antigens
- Wash out the well
- A secondary antibody with attached enzyme is added
- Wash out the well
- Substrate is added and for a positive result of the disease there will be a colour change
What does HIV stand for ?
Human Immunodeficiency Virus
What does AIDS stand for?
Acquired Immune Deficiency Syndrome
What are the structures found in HIV?
- Reverse Transcriptase
- RNA genome
- Attachment proteins
- Capsid
- Lipid envelope
What is the role of reverse transcriptase?
Enzyme that converts the RNA genome of HIV into double stranded DNA
What is the role of attachment proteins?
- Act as antigens to host immune system
- Helps virus attach to and get into and infect the host cell ( T helper)
How does the invasion by a HIV into a t-helper cell affect the immune response?
- Infected T helper cells will not function therefore there will be less of them
- Less clonal selection and replication therefore fewer specific complimentary antibodies are produced by plasma cells
What is the envelope on HIV made of?
It is a phospholipid bilayer that is derived from the host cell’s surface membrane
Describe the steps in HIV replication.
- Attachment protein attaches to a receptor molecule on the cell membrane of a host cell
- Capsid is released into the cell, where it uncoats and releases the RNA into the cell’s cytoplasm
- Reverse transcriptase is used to make a complimentary strand of DNA from the viral RNA template
- Double stranded DNA is made and inserted into the human DNA
- Host cell enzymes and ribosomes are used to make viral proteins from the viral DNA found within the human DNA
- Viral proteins assembled into new viruses, which bud from the cell and go on to infect other cells
What can the immune response be split into?
- Cellular and Humoral
What does the humoral response consist of?
B-cells, clonal selection and the production of monoclonal antibodies
What does the Cellular (cell mediated) response consist of?
T cells, other immune system cells eg. phagocytes
Describe how a secondary immune response differs to a primary immune response
A secondary immune response is a faster and stronger response because memory cells are produced during the primary response , which are able to recognise the foreign antigen when it is encountered again.
- During the second infection, memory B cells can quickly divide to form plasma cells which secrete the correct antibody to the antigen
- Memory T cells quickly divide into the right type of T cells to kill the cell carrying the antigen
What are the differences between active and passive immunity?
Active requires exposure to an antigen whereas passive doesn’t
Memory cells are produced during active immunity whereas there isn’t any formed during passive immunity
It takes a while for protection to develop during active immunity whereas it is immediate during passive.
What is herd immunity?
When some individuals in a population receive the vaccine, the occurrence of the disease in the population is reduced. This means that those in the population who haven’t been vaccinated are less likely to become infected. This is called Herd immunity
Explain why it is possible to suffer from the flu more than once?
The flu virus is able to change its surface antigens which means that when you get infected the second time, the memory cells produced during the primary response will not recognise the new foreign antigens. Therefore the immune system must carry out primary response again, this takes time so you will become ill.
Explain why active immunity offers long-term protection against disease, whereas passive immunity only offers protection for a short term?
Active immunity involves the production of memory cells specific to a particular antigen, this means that the immune system is able to mount a secondary immune response if the same antigen is detected again. Passive immunity only offers short term protection because the antibodies given are broken down in the body. Memory cells are not produced, so the body cannot mount a secondary immune response
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