Cell recognition and the immune system Flashcards
What is a pathogen?
A disease causing microorganism
What is immunity?
The bodys ability to kill a pathogen before it causes any harm
What are the two types of white blood cell?
- Lymphocyte
- Phagocyte
What are the two types of lymphoctye?
T and B
Why must white blood cells be able to distinguish between cell and non cell?
Allows the white blood cell to know what is part of your body and what is not so the bodys own tissues are not destroyed
What is used to identify cells as self and non self?
Proteins on the cell surface membrane
Why are proteins used to identify where cells are self or non-self?
Huge variability and the tertiary structure is very specific
What are the immune system able to identify?
- Pathogens
- Non-self material
- Toxins
- Abnormal body cells
What name is given to the protein which causes an immune response?
Antigen
What issues may arise with the immune system, due to transplants?
May recognise the tissues as non-self and attack them
What are the 2 types of defence?
Specific and non specific
What are the 2 types of non-specific defense?
Physical barrier and phagocytosis
What are the 2 types of specific defense?
Cell mediated and humoral response
What types of cells are involved in cell mediated response?
T lymphocytes
What types of cells are involved in humoral response?
B lymphocytes
Why do lymphocytes not attack our own body?
- As a foetus, our lymphocytes were only exposed to our own cells, those which combined were destroyed leaving only those which fit foreign material.
- As an adult, lymphocytes are created in the bone marrow and only encounter self antigens. If an immune response is triggered, the cell kills itself.
What is the role of a phagoctye?
To ingest and destroy pathogens
What is phagocytosis?
Ingesting of large particles into vesicles by the cell surface membrane
What allows phagocyte to recognise and attach to chemicals on the surface of a pathogen.
Receptors on the cell surface membrane
When the pathogen is engulfed, what is the vesicle called?
Phagosome
What fuse with the phagosome?
Lysosome
What do the lysosomes contain and what do they do to the pathogen?
Hydrolytic enzymes (lysozymes) which break down the pathogen
What happens after the pathogen has been digested in the pagosome?
Soluble products are absorbed into the cytoplasm of the phagocyte
What is cell mediated immunity?
Response of T-lymphocytes to foreign antigens
What is an antigen?
Part of an organism which is recognised as non-self and stimulates and immune response
What form do most antigens take?
Proteins on the cell surface membrane
Which white blood cell is involved in the specific immune response?
Lymphocytes
Where are the two types of lymphocytes made and matured?
T- made in the bone marrow, and matured in the thymus gland
B- made and matured in the bone marrow
What role do B- lymphocytes play in the immune system?
Associated with the humoral immunity. Has antibodies
What role do T-lymphocytes play in the immune response?
Associated with cell mediated immunity.
How are T-lymphocytes able to identify invader cells from normal cells?
Phagocytes present antigens of hydrolysed pathogens on their surface membrane
Why are there a vast number of different T cells?
Each T cells receptors corresponds to one specific antigen. There needs to be a variety of T cells to respond to the variety of antigens
In what way might cloned Th ccells differentiate?
- Develop into memory cells
- Stimulate phagocytosis
- Stimulate B cells to divide and secrete antibodies
What chemical do cytotoxic T cells produce?
Perforin
How does perforin kill pathogens?
Makes little holes in the membrane making it freely permeable and killing it
What pathogens do Tc cells work best against?
Viruses as they only replicate when in host cells so if the host cell dies replication can no longer occur.
What is meant by humoral immunity?
Second stage of an immune response, causing B cells to produce antibodies which dissolve into the blood and tissue fluid.
Why are there million types of B cell?
Each one creates a specific antibody to respond to a specific antigen.The variations in antigens require a large number of antibodies
What does a B cell do to the antigen when it has attached the antibody to its surface?
Taken in by endocytosis and then presented on the surface becoming an APC
How is a B cell stimulated to divide by mitosis?
Activated Th cell binds to the processed antigens on the B cell to stimulate it to divide, creating clones and this is clonal selection
Why are more than one type of B cell activated for division?
Each pathogen typically has many proteins on its surface membrane acting as antigens. They also produce toxins. All of these can stimulate a B cell to divide
What are the antibodies created from B cell clones described as?
Monoclonal antibodies
What can the B cell clones differentiate into?
Plasma cells and memory cells
What do plasma cells do?
Primary immune response. They create a specific antibody. It is secreted into blood plasma.
What do memory cells do?
Secondary immune response. They last a long time in the body. Stimulated to divide rapidly.
Why is the secondary immune response much faster and of a greater magnitude than the primary immune response?
Primary response relies on the activation of both the specific Th cells and B cells before antibodies can be released. The secondary immune response needs only the memory cells
What is an antibody?
Protein created by a B cell, it has two identical, specific, binding sites
What do antibodies do?
Binds to a specific antigen, which is complementary to its specific binding site
What are antibodies made of? What is their basic structure?
Made of 4 polypeptide chains. 2 long 2 short (light)
What is the name given to the binding site of an antibody?
Variable region because it is specific
What causes the variable region of an antibody to be different?
Sequence of amino acids that form a specific 3D shape
What is the part of the antibody which is not different?
Constant region
Do antibodies destroy pathogens?
Not directly. They cause agglutination through binding two pathogens at once. They also act as markers to stimulate phagocytosis
How are monoclonal antibodies used to treat disease?
Direct monoclonal antibody therapy and indirect monoclonal antibody therapy
How does direct monoclonal therapy work?
Monoclonal antibodies are created which will attach to specific antigens on cancer cells. These are given to the patient and attach only to the cancer cells receptors. This blocks the signals to stimulate uncontrolled division
How does indirect monoclonal therapy work?
Monoclonal antibodies are created which will attach to specific antigens on cancer cells. A cytotoxic drug is on the antibody and given to the patient and only attach to cancer cell receptors, killing the cell.
What are the benefits of using monoclonal therapy>
Produce results very quickl.
How are monoclonal antibodies used in pregnancy tests?
Pregnant women produce HCG hormone. Test strip has three parts to is:
- 1st contains antibodies complementary to HCG
- 2ND contains antibodies complementary to HCG-Antibody complex
- 3rd contains antibodies complementary to HCG antibodies so even if not pregnant a blue line will show (control)
What are the two types of immunity?
Passive and active
What are the two types of active immunity?
Natural and artifical
What is passive immunity?
Antibodies are given to the person, the body is not creating them
What is active immunity?
The body responds to antigens stimulating antibodies
What is natural active immunity?
When a person is infected with a particular disease their body responds as normal
What is artificial active immunity?
A person is given a vaccination causing an immune response
What does a vaccine contain?
One or more types of antigen from the disease causing pathogen
What is the most important result of vaccination?
Creation of memory cells
What is a vaccination programme?
Delivery of a vaccination to the population
What makes a vaccination programme successful?
Economical to produce large volumes
What is herd immunity?
Allows those unvaccinated to stay safe
Why is herd immunity so important?
Certain people such as babies or sick people can not be vaccinated
Why might vacciniation not eradicate a disease?
Pathogen may mutate so rapidly that vaccines will stop working.
Some people will not develop immunity
What are the ethical concerns of vaccinations?
Use of animals in their production
What is HIV?
The human immunodeficiency virus that can develop into AIDS.
What are the components of HIV?
- Lipid envelope
- Attachment protein
- Capsid
- RNA
- Enzymes
What group of viruses does HIV belong to?
Retroviruses
How does HIV replicate?
Uses the host cell to create the component parts
Why does HIV damage the immune system?
HIV viruses’ attachment proteins specifically bind to receptors on Th cells and so these cannot stimulate B cells or cytotoxic T cells. Memory cells cant be formed either
Why is HIV indirectly dangerous?
As the virus damages the immune system, the individual cannot respond to the new pathogens well
What is the test used to identify the presence of specific proteins?
ELISA test
What does ELISA stand for?
Enzyme linked immunosorbant assay
What can the ELISA test be used for?
Identifying the presence of pathogens or drugs where the quantity of the substance is more important than its presence
What is a way that antibiotics work?
Stops the production of the cell wall of a bacteria
Why is the cell wall of a bacteria so important?
Stops the destruction of the cell via osmotic lysis
What is the cell wall of a bacteria made of?
Meurin
How would the inhibition of enzymes building the cell wall cause the bacterium to die?
If the cell wall is not as strong, it will not withstand the outward forces caused through the movement of water by osmosis. The influx of water can cause the cell to break apart
What are the different reasons by which the antibiotics can not affect viruses?
- Do not carry out metabolic processes, so these cannot be stopped
- Do not have a meurin wall
- Hidden within the hosts cell
