Chapter 5 - Cell Recognition And The Immune System Flashcards
What are antigens
Proteins on the surface of cells which cause an immune response
Why are antigens useful
They allow the immune system to recognise
- Pathogens
- Cells from the same species (allowing organ transplant)
- Abnormal body cell eg tumour
- Toxins
What are antibodies
Proteins that bind to antigens to kill pathogens
What is a pathogen
An organism that causes disease
What are examples of pathogens
Bacteria, fungi, virus
How does a pathogen cause disease
- Destroying host cells
- Or producing toxins
What are the parts of the cellular immune response
Phagocytosis
T-Cells
What is phagocytosis
The first line of defence
Not specific to any pathogen
What happens in phagocytosis
- Phagocyte identifies foreign antigen (on a pathogen)
- Engulfs pathogen into phagocytic vacuole
- releases lysosomes
- which hydrolyse the pathogen
- Phagocyte presents the antigens on its surface
- So is an antigen presenting cell
- Stimulates the rest of the immune response
What are T cells also known as
T-lymphocytes
How are T cells activated
By antigens presented on phagocyte
What are the 2 types of T cells
T helper cells
Cytotoxic T cells
What do t helper cells do
Activate B cells and cytotoxic T cells
What do cytotoxic T cells do
Kills cells infected by a pathogen
What does a B do
Produce a specific antibody
What does a B cells antibody do
- Forms antigen-antibody complex with complementary antigen
- Activates the selection of the correct B cell
- This divides/clones itself
- Into many copies called plasma cells
- This is clonal selection
What is clonal selection
Where only the specific B cell that forms an antigen-antibody complex is selected to divide into plasma cells
What are plasma cells
Clones of the selected B cell with complementary antibodies to the pathogens antigen
What do plasma cells do
- Make monoclonal antibodies
- These form antigen-antibody complex with antigen
- Sticks pathogens together, known as agglutination
- Phagocytes can destroy more pathogens at once (more efficient)
- When infection is over, plasma cells are saved as memory B cells
Draw and label an antibody
Picture on snapchat memories 14 nov
Explain characteristics of antibodies
Proteins that have:
- A specific primary structure
- Specific tertiary structure
- Variable region that is complementary to antigen
Explain the primary response to infection
- The first immune response
- Slow to occur, as it includes phagocytosis, T cells, B cells, and plasma cells
- Pathogen multiplies so symptoms are felt
- After infection, memory cells are saved
Explain the secondary response to an infection
- Pathogen with same antigen infects you for a second time
- Immune response is faster and stronger
- Only need memory B cells to divide into plasma cells which make antibodies for humoral response
- Memory T cells kill pathogens (cellular response)
- No symptoms felt
Draw graph showing primary and secondary response to infections and explain each part
Snapchat memories 14 nov
What are monoclonal antibodies
Identical antibodies made from the same B cell/plasma cell
What are the 2 functions of monoclonal antibodies
- Targeting medication
- Medical diagnosis
Explain how monoclonal antibodies can be used to target medication
- Can be used to deliver drugs
- All cells have specific antigens on their surface
- Drug can be attached to complementary monoclonal antibody (of cells antigens)
- Forms antigen-antibody complex
- Drug can carry out function when arrives at cell eg tumour cell
How can monoclonal antibodies be used for medical diagnosis
Eg testing for a disease
- Fix monoclonal antibodies to a plate
- Add sample of ??
- Antigen-antibody complexes will be formed if antigen is present in sample
- Rinse plate to remove inbound antigens
- Add monoclonal antibody with a colour or enzyme attached (marked)
- Rinse again
- Observe to look for marker, if enzyme attached to substrate there will be a colour change???
What are vaccines
Something containing antigens from a dead or weakened pathogen
How do vaccines lead to immunity
- Vaccine stimulates immune response eg antibodies/plasma cells/memory cells
- If you become infected with pathogen a secondary response will occur and so no symptoms will be experienced
What is meant by herd immunity
When a higher percentage of a population is immune, there are fewer people to pass on the disease and so risk is reduced for everyone
How are vaccines taken
Usually by injection
But can be orally
What is meant by antigenic variability
Where antigens in the surface of pathogens change/vary as pathogens have different strains
How does antigenic variability influence vaccination
- New antigen May not be complementary to antibody made by memory cells
- Therefore if infected again, primary response will occur and symptoms will be felt
What is meant by active immunity
When the body makes its own antibodies as a result of being infected
What is meant by passive immunity
When you’re given antibodies by another organism
What are the 2 types of active immunity
Natural active immunity
Artificial active immunity
What is the difference between natural and artificial active immunity
Natural is through infection, primary response etc
Artificial is through vaccination and thus memory cells
What are the key features of active immunity
- Slow process
- Long term as memory cells last forever
- Have to be exposed to antigen
What is natural passive immunity
What antibodies are given to children by their mother
Eg through placenta or breast milk
What is artificial passive immunity
When you are given someone else antibodies eg through blood transfusion
What are the key features of passive immunity
- Fast/immediate protection
- May only last short term as foreign antibodies may be broken down by body
- Doesn’t make memory cells
- No exposure to antigen
What is the ELISA test
A test to see if patients have a specific antibody or antigen
What does ELISA stand for
Enzyme Linked Immuno Sorbet Assay (test)
What are the 2 types of ELISA test and what are they testing for
Direct ELISA - Test for antigens
Indirect ELISA - Test for antibodies
Explain direct ELISA test
- Immobilised antibodies are attached to a well (plate)
- Sample added (eg blood plasma)
- If it contains antigen, a-a complex will be formed
- Rinse to remove unbound antigens
- same Antibody with an enzyme attached is added
- Rinse to remove inbound antibodies and enzyme
- Add substrate, if there is a colour change it is positive, because substrate will have attached to enzymes which will mean antibodies are present and have attached to antigens
Explain indirect ELISA test
- Antigens are attached to a well (plate)
- Sample added
- If contains complementary antibody, a-a complexes will be formed
- Rinse to remove unbound antibodies
- a different antibody is added with an enzyme attached
- This will only bind if the first antibody is present
- Rinse to remove unbound antibodies and enzyme
- Add substrate, colour change of present
What does HIV stand for
Human Immunodeficiency Virus
When infected be HIV, what does it do
Attaches to t helper cells, uses them as host cells
How does HIV cause AIDS to develop
- Kills or interferes with t helper cells
How does AIDS cause bad health
- T helper cells can’t function
- Immune system can’t stimulate B cells to produce antibodies or cytotoxic T cells to kill infected cells
- Body can’t produce an adequate immune response to future infections
- These infections can therefore lead to a deterioration in health and possible death
Explain the structure of HIV, using 5 main parts
- LIPID ENVELOPE on outside
- ATTACHMENT PROTEINS are embedded in this
- Inside envelope is a protein layer called the CAPSID
- This encloses two single strands of RNA and enzymes such as REVERSE TRANSCRIPTASE (that catalyses the production of DNA from RNA)
How does HIV replicate
- A virus is acellular so needs a host cell
- Attachment protein on HIV bonds to a protein called CD4, which can be found on t helper cells
- The HIV reverse transcriptase converts the virus’s RNA into DNA
- Newly made DNA enters T cells nucleus through nuclear pore, where it’s inserted into DNA of cell
- HIV DNA creates mRNA which contains instructions for new viral proteins and RNA for new HIV
- mRNA passes out of nucleus through pore and uses cells protein synthesis mechanisms to make new HIV
- HIV breaks always from T helper cell, taking a price of its cell surface membrane which they use to form their lipid envelope
What are the parts of the hunoral response
B cells
Plasma cells
