2.4: Immunolgy Flashcards
What can the immune system identify as non self?
- Pathogens
- Cells from other organisms
- Abnormal body cells
- Toxins
What is the specific response in white blood cells?
Lymphocytes
What is the non-specific response in white blood cells?
Phagocytes
What is a phagocyte?
Type of white blood cell
Describe phagocytosis
1) Phagocytes are attracted to chemicals released by pathogens
2) Phagocytes attach to pathogens by receptors and phagocytes engulf the pathogen
3) Pathogen contained in. a phagosome vesicle
4) Lysosome fuse with phagosome and releases lysozyme
5) Lysozyme enzyme hydrolyses pathogen
Define antigen
A molecule (protein) that stimulates an immune response that results in the production of a specific antibody
What is a macrophage?
A cell that has engulfed and destroyed a pathogen and presents the antigens on the surface
What is an antigen presenting cell?
Any cell that presents a non-self antigen on their surface
What is the cell mediated response?
Involving T cells and body cells
Describe the cell mediated response
1) Phagocyte engulfs and hydrolyses pathogen and presents antigen on cell surface membrane
2) TH cell with specific receptor binds to presented antigen
3) Once attached this activated TH cells to rapidly clone by mitosis
4) Cloned TH cells differentiate into more TH cells, memory cells and cytotoxic T cells
What are cytotoxic T cells?
-destroy infected or abnormal body cells
How do cytotoxic T cells cause cell death?
Release protein called perforin which creates pores in cell surface membrane so any substances can enter and leave the cells
What are cytotoxic T cells most common in viruses?
Viruses affect body cells so these cells are sacrificed to prevent viral replication.
What is the humoral response?
Involves the activation of B cells to produce antibodies.
Role of memory B cells
Remain in body to rapidly and extensively respond to pathogen in case of future re-infection (active immunity)
What are the roles of TH cells?
- release cytokines to attract phagocytes
- release cytokines that activate cytotoxic T cells
- Active specific complementary B cells
- Form memory cells
Describe B cell activation
1) Specific TH cell binds with correct receptors to presented antigens and locates and activates a specifically complimentary B cell to clone by mitosis
2) Cells differentiate into plasma cells or memory B cells
Role of plasma cells
Secrete vast quantities of specific antibodies into the blood plasma
What is the secondary response?
The activation of memory cells to produce antibodies
Define antibody
Protein made in response to a foreign antigen with binding sites which bund specifically to an antigen.
Antibody structure
- Quaternary structure (4 polypeptide chains)
- Constant region
- Variable region - different primary and tertiary structure so has binding site which is specific to a specific antigen
- Heavy chain (longer)
- Light chain (shorter)
- Disulfide bridge between R groups
Agglutination
Specific antibodies bind to antigens on pathogen and clump them together to make phagocytes locate them easily and be destroyed
What is passive immunity
1) Antibodies are given
2) No exposure to antigen
3) No memory cells are produces
4) Short term
5) Fast acting
Describe how vaccinations work
- contains weakened/dead antigen from pathogen
- Phagocyte presents antigen on its surface
- Specific TH cell with specific receptor binds to complementary antigen
- TH cell stimulates specific B cell
- With complementary antibody on its surface
- B cell divides by mitosis to form plasma cells
- Plasma secrets large amount of antibodies
- Formation of memory B cells with complementary antibodies remain in the blood
What is active immunity
1) Antibodies are produced
2) Exposure to antigen
3) Memory cells produced
4) Long term
5) Takes time to develop
Define herd immunity
If enough individuals in the population are vaccinated then there is a little chance of disease spreading therefore even non-vaccinated individuals are protected
HIV structure
1) core = genetic material, RNA, and reverse transcriptase (viral replication)
2) Capsid = Outer protein coat
3) Envelope = Extra outer layer made from host cells membrane
4) Protein attachments = so virus attaches to hosts TH cell
Describe antigenic variability
- gene mutation in pathogen may lead to change in tertiary structure of antigens specific to B cell
- Memory B cell no longer complementary to mutated pathogen so no antigen-antibody complex will form
- no secondary response
HIV replication
1) Attachment proteins on HIV bind with protein receptor on TH cell
2) Capsid fuses with membrane and releases viral RNA and enzymes into TH cell
3) Reverse transcriptase converts viral RNA into complementary DNA using hints nucleotides. Complementary DNA converted into double stranded DNA by DNA polymerase
4) Viral DNA moves into nucleus of TH cell and inserted into hats genome. Cell is infected
5) Viral DNA transcribed into viral mRNA
6) Viral mRNA translated into HIV proteins. TH cell makes HIV virions
7) Virions break away from TH cell with section of host cell membrane which forms lipid envelope with TH cells receptors embedded
How can aids be checked?
Checking the number of TH cells
How does HIV affect the body?
Reduces an individuals ability to respond to pathogens as their cell mediated immunity is compromised. Leaves people vulnerable to secondary diseases which can cause death. B cells must be activated by specific TH cells which may have been destroyed
How do antibiotics work?
- prevent bacteria from making a cell wall (murine) by targeting 70s ribosomes so bacteria is unable to resist osmotic presses and cells burst due to increase in cell volume of water by osmosis
Why does antibiotics not work on viruses?
- Viruses have capsid (protein coat) instead of murein cell wall so antibiotics can’t act on viruses like bacteria
- Viruses replicate inside host cell so are out of reach
What is a monoclonal antibody
Single type of antibody that can be isolated or cloned
How are monoclonal antibodies used for targeted medication (direct) (example of cancer cells)
- Monoclonal antibodies are designed with a binding site complementary in shape to antigens outside of cancer cells
- antibodies given to patients, attach to cancer cells which prevents chemicals binding to cancer cells which enable uncontrolled cell division
- Prevents cancer cells growing as they don’t attach to normal cells
How are monoclonal antibodies used for targeted medication (indirect) (example of cancer cells)
- Monoclonal antibodies complimentar in shape to antigens outside of cancer cells which have drugs attached to them
- Cancer drugs directly delivered to cancer cells and kill them
indirect ELISA
1) Antigen coated well
2) Wash to remove unbound sample
3) Add antibody complementary in shape to antigen
4) Wash to remove unbound antibodies
5) Add a second antibody with enzyme attached which is complementary to first antibody so they bind together
6) Substrate for enzyme, colourless, added. Substrate produces colour in presence of enzyme
Ethics of monoclonal antibodies
- animals used
- animals genetically engineered to produce monoclonal antibodies
