Immune response Flashcards
Is phagocytosis specific or non specific?
non specific
Define antigen
protein which can generate an immune response
Define pathogen
organisms that cause disease
Describe phagocytosis
- A phagocyte recognises the foreign antigens on a pathogen
- Engulfs it
- The pathogen is now in a phagocytic vacuole in the cytoplasm
- A lysosome fuses with the vesicle and the lysozymes break down the pathogen
- Any unused parts will be dealt with by the lymphatic system
- The phagocyte then presents the pathogens antigens to become an antigen presenting cell
Describe cell mediated response
- Happens by T lymphocytes or cytotoxic T cells
- Happens inside the cells
- The antigen presenting cells are approached by helper T cell which is complimentary
- It binds to the antigen presenting cell
- This then activates the relevant cytotoxic T cell which then divide by mitosis
- Cytotoxic T cells produce perforin
- This attacks the pathogen and makes the membrane of the cell freely permeable
- It had perforated the cell membrane and kills the cell
- Some T cells will divide via mitosis to form memory T cells
Describe the humoral response
-B lymphocytes and happens in the bloodstream
- Antigens in the blood collide with their complimentary antibody on a B cell
-The B cell then takes in the antigen via endocytosis and presents it on the surface membrane
- When this B cell collides with a helper T cell receptor, this activates the B cell to go through clonal selection
- They undergo mitosis to form lots of plasma B cells and memory B cells
- Memory B cells need to be maintained in the bloodstream
- Plasma B cells make antibodies
- B memory cells can divide rapidly into plasma cells when reinfected with the same pathogen
Explain how HIV targets cells
- Targets cells as they can bing to the helper T cells - they bind to receptors called CD4 receptors
- Cells end up bursting and destroying helper T cells which means they cannot activate an immune response
What happens when T cell level gets too low?
AIDS
What are in the capsid of HIV?
RNA and enzymes
The enzyme is reverse transcriptase which make RNA into DNA
What are the attachment proteins for on HIV?
To attach to CD4 receptors on the helper T cells
Describe HIV replication
- The attachment protein attached to a receport molecule on the helper T cell
- The capsid is released into the cell where it unwinds and releases genetic material
- Reverse transcriptase is used to make a complimentary strand of DNA from RNA template
- Double stranded DNA is made and inserted into human DNA
- Host cell enzymes are used to make viral proteins from the viral DNA
- They produce so many that the cell bursts and the viral proteins get released into the bloodstream and can do the same to lots of other cells
Describe the ELISA test
- relies on antibodies binding with HIV
- HIV antigen is bound to the bottom of the well in a well plate
- Then get a sample of blood from the patient as if they have HIV they will be producing antibodies against HIV and add this to the well
- If they have HIV the antibodies will bind
- Wash out the well to remove any unbound antibodies
- A secondary antibody which is complimentary to the first antibody is added - attached to an enzyme
- This can bind to the HIV -specific antibody and the well is washed out again
- A solution is added to the well - it contains a substrate which reacts with the enzyme attached to the secondary antibody to produce a coloured product
Describe the structure of an antibody
- Each antibody has a different variable region
- They are proteins
- Tertiary structure of all antibodies have to be different
-Chains are connected by disulfide bridges
What is agglutination?
means that the pathogens are gathered together and clumped into one space
efficient process
more noticeable to the phagocytes as all together
the phagocytes then come and destroy them
Describe antigenic variation
Pathogen mutate and change their surface antigens. This means that memory cells will not work and vaccines will need updating.
