2C - Cells And The Immune System Flashcards
What are antigens?
Proteins on the surface of cells that can generate an immune response when detected by the body.
What can antigens allow the body to recognise?
- Pathogens
- Abnormal body cells
- Toxins
- Cells from other individuals of the same species
What are pathogens?
Organisms that cause disease.
What is the difference between T-cells and T-lymphocytes?
Nothing, they are the same thing (a type of white blood cell).
Are specific lymphocytes produced in response to an infection?
- No, they all already exist.
- There are many different types -> Only a few will match the pathogen’s antigens.
- The ones that match are stimulated to divide -> Clonal selection.
What are the types of defence mechanism against infection?
- Non-specific -> Physical barrier + Phagocytosis
* Specific -> Cell-mediated response + Humoral response
What is the difference between the non-specific and specific immune response?
- Non-specific -> Immediate and the same for all pathogens
* Specific -> Slower and specific to each pathogen
What are the different types of white blood cell?
- Phagocytes
* Lymphocytes -> T-cell + B-cell
What are phagocytes?
A type of white blood cell that ingest and destroy pathogens (phagocytosis).
What are lymphocytes?
White blood cells involved in the specific immune response.
What is phagocytosis?
The process by which phagocytes engulf and digest pathogens.
Describe the process of phagocytosis.
1) Phagocyte is attracted to the pathogen by its chemical products + moves along the concentration gradient towards it.
2) Phagocyte attaches onto the pathogen’s antigens.
3) Cytoplasm moves around the pathogen + forms a phagosome.
4) Lysosomes in the phagocyte migrate towards the phagosome and release lysozymes into it.
5) Lysosomes hydrolyse the pathogen + the products are absorbed by the phagocyte.
6) Phagocyte displays antigens on the cell surface to activate other cells.
What is a phagosome?
The “bubble” that is formed around the pathogen when a phagosome engulfs it.
What are lysosomes and lysozymes?
- Lysosomes -> Sacs that contain lysozymes.
* Lysozymes -> Enzymes that break down (hydrolyse) forgein material.
Compare how quickly non-specific and specific immune response happens.
Non-specific is faster, but specific provides long-term immunity.
What is another name for B lymphocytes?
B cells
What is another name for T lymphocytes?
T cells
Are phagocytes and lymphocytes part of the specific or non-specific immune response?
- Phagocytes -> Non-specific
* Lymphocytes -> Specific
Where are lymphocytes produced?
By stem cells in the bone marrow.
What is the cellular immune response?
The T-cells and other immune system cells that they interact with -> e.g. Phagocytes
What is the humoral immune response?
B-cells, clonal selection and the production of monoclonal antibodies.
What type of cells is the cellular immune response associated with?
T-cells
What type of cells is the humoral immune response associated with?
B-cells
What are the two parts of immune response?
- Cellular
* Humoral
What is another name for cellular response?
Cell-mediated response
How can T-cells distinguish harmful cells and pathogens from normal body cells?
- Phagocytes that have engulfed and hydrolysed a pathogen present some of a pathogen’s antigens on their own membrane
- Body cells invaded by a virus present some of the viral antigens on their membrane
- Transplanted cells from the same species have different antigens on their membrane
- Cancer cells present antigens on their membrane
What do T-cells do in the immune response?
• Receptor proteins on the helper T-cell surface bind to complementary antigens presented by phagocyte
• This activates the helper T-cell to divide by mitosis.
• Cloned cells:
1) Become memory T-cells -> Allow rapid response in the future
2) Stimulate phagocytosis
3) Stimulate B cells to divide and secrete antibodies
4) Activate cytotoxic T cells
Which T-cells are first to respond in the immune response?
Helper T-cells
Are all helper T-cells the same?
- No, each type has different receptors that respond to a different antigen.
- Only the ones that bind to the antigen presented by the phagocytes divide by mitosis.
What do cytotoxic T-cells do?
- Produce a protein called perforin
* Perforin makes holes in the cell-surface membrane
What protein do cytotoxic T-cells make?
Perforin
Describe the entire cellular immune response.
PHAGOCYTES:
• Phagocytes engulf and digest pathogens by phagocytosis
• Present antigens on their surface
HELPER T-CELLS:
• Receptor proteins on surface bind to complementary antigens presented by phagocyte
• This activates the helper T-cell to divide by mitosis.
• Cloned cells:
1) Become memory T-cells -> Allow rapid response in the future
2) Stimulate phagocytosis
3) Stimulate B cells to divide and secrete antibodies
4) Activate cytotoxic T cells
CYTOTOXIC T-CELLS:
• Produce perforin
• Perforin produces holes in cell membranes
Name the types of cell involved in the cellular immune response.
• Phagocyte
• Helper T-cell
• Cytotoxic T-cell
(• Memory T-cell)
Are are B-cells the same?
- No, each type has different antibodies on its surface.
- Only the ones that produce (and have on their surface) the antibody that is complementary to the pathogen’s antigens will be activated by helper T-cells to divide.
What do B-cells do in the cellular immune response?
• Antigens on the pathogen bind to complementary antibodies that cover the B-cell
• Antigens are engulfed by the B-cell by endocytosis + presented on the cell surface
• Helper T-cells bind to the antigen on the cell-surface and activate the B-cell
• B-cell divides by mitosis to form plasma cells or memory cells (clonal selection)
PLASMA CELLS (Primary response):
• All produce the antibody that is specific to the foreign antigen
• Antibodies
MEMORY CELLS (Secondary response):
• Allow a faster immune response in case of second infection
• Do not produce antibodies but rapidly divide to give plasma and memory cells if encounter the antigen
What is clonal selection?
Check with teacher
The process by which a B-cell with the specific antibody for a particular antigen is stimulated to divide and the body can produce antibodies for that antigen rapidly.
Name the types of cells involved in the humoral immune response.
• B-cell (+ plasma cell)
• Memory B-cell
What are plasma cells?
- Cloned versions of a B-cell, produced when a specific B-cell is stimulated to divide.
- Produce monoclonal antibodies that are specific to an antigen.
- Have a short lifespan.
What is the difference between memory T-cell and memory B-cells?
Ask teacher
What are memory B-cells?
- Cloned versions of a specific B-cell
- Allow a quick response in case of second infection -> Do not produce antibodies but rapidly divide to give plasma and memory cells if encounter the antigen
- Have a long lifespan.
Describe the entire humoral immune response.
B-CELLS:
• Antigens on the pathogen bind to complementary antibodies that cover the B-cell
• Antigens are engulfed by the B-cell by endocytosis + presented on the cell surface
• Helper T-cells bind to the antigen on the cell-surface and activate the B-cell
• B-cell divides by mitosis to form plasma cells or memory cells (clonal selection)
PLASMA CELLS (Primary response):
• All produce the antibody that is specific to the foreign antigen
• Antibodies
MEMORY CELLS (Secondary response):
• Allow a faster immune response in case of second infection
• Do not produce antibodies but rapidly divide to give plasma and memory cells if encounter the antigen
Describe the entire immune response.
PHAGOCYTES:
• Phagocytes engulf and digest pathogens by phagocytosis
• Present antigens on their surface
HELPER T-CELLS:
• Receptor proteins on surface bind to complementary antigens presented by phagocyte
• This activates the helper T-cell to divide by mitosis.
• Cloned cells:
1) Become memory T-cells -> Allow rapid response in the future
2) Stimulate phagocytosis
3) Stimulate B cells to divide and secrete antibodies
4) Activate cytotoxic T cells
CYTOTOXIC T-CELLS:
• Produce perforin
• Perforin produces holes in cell membranes
B-CELLS:
• Antigens on the pathogen bind to complementary antibodies that cover the B-cell
• Antigens are engulfed by the B-cell by endocytosis + presented on the cell surface
• Helper T-cells bind to the antigen on the cell-surface and activate the B-cell
• B-cell divides by mitosis to form plasma cells or memory cells (clonal selection)
PLASMA CELLS (Primary response):
• All produce the antibody that is specific to the foreign antigen
• Antibodies
MEMORY CELLS (Secondary response):
• Allow a faster immune response in case of second infection
• Do not produce antibodies but rapidly divide to give plasma and memory cells if encounter the antigen
Remember to practice drawing out a flowchart for the entire immune response.
Textbook pgs 104-110 + Revision guide pg 44
What are antibodies?
- Proteins with specific binding sites produced by B-cells.
* Bind to antigens to produce antigen-antibody complexes.
What type of molecule are antibodies?
Proteins
What happens when an antibody binds to antigen?
- Antigen-antibody complex forms
* If an antibody binds to two antigens, they clump together -> Agglutination
Describe the structure of an antibody.
- 2 long inner HEAVY chains
- 2 shorter outer LIGHT chains
- Variable regions at the top of each chain -> Binding site between the tops of a light and heavy chain
What joins the two heavy chains in an antibody?
Disulfide bridge
What causes the two heavy chains in an antibody to bend?
Hinge protein
Where are the constant and variable regions in an antibody?
- Constant -> Bottom parts of each chain
* Variable -> Top parts of each chain
How many binding sites are on an antibody?
Are they the same?
- 2
* Yes
In an antibody, are the light or heavy chains longer?
Heavy
Where are the binding sites on an antibody?
At the variable regions at the top of each pair of chains.
What are the 4 chains in an antibody?
Polypeptide chains
What determines the specificity of an antibody?
The tertiary structure of the variable region of the polypeptide chains.
Is the constant region the same in each antibody?
Yes
Remember to practise labelling an antibody.
Pg 44 of revision guide.
Do antibodies destroy antigens?
No, they prepare the antigen for destruction.
How do antibodies help in the immune response?
1) Bind to two pathogens at once -> Agglutination -> Allows phagocytes to phagocytose many pathogens at once
2) Serve as markers that stimulate phagocytes to engulf the cells they are attached to
What are monoclonal antibodies?
Antibodies produced from a single group of genetically identical B-cells.
What is the primary immune response?
- The immune response when an antigen enters the body for the first time.
- Involves the production of antibodies and memory cells.
- It is slow.
What is the secondary immune response?
- The immune response that occurs when an antigen enters the body for the second time.
- Involves memory B-cells dividing into plasma cells and memory T-cells dividing into the correct type of T-cells.
- It is fast.
Explain the difference in speed of the primary and secondary response.
- Primary -> Slow -> Aren’t many B-cells that can make the antibody needed.
- Secondary -> Fast -> Memory B-cells and memory T-cells are ready to divide and fight the disease -> Antibodies produced faster.
Will there be symptoms during the primary and secondary immune response?
- Primary -> Yes
* Secondary -> Probably not
How do memory B-cells and memory T-cells work when activated?
- Memory B-cells -> Divide into plasma cells and memory B-cells -> Plasma cells produce the right type of antibody
- Memory T-cells -> Divide into the correct type of T-cells to kill the cell carrying the antigen
What causes the secondary immune response to be different from the primary?
- The primary immune response involves producing memory T-cells and memory B-cells.
- These allow for a faster secondary immune response.
What is immunity?
A system’s ability to quickly respond to a specific infection before it can cause harm.
Describe the graph for “concentration of the right antibody in the blood” (y) against time (x) for the primary and secondary response.
Primary response:
• Slower response after exposure -> Peak rises after more days + slow rise
• Lower peak height
• Doesn’t necessarily fall back to near 0 antibody concentration
Secondary response:
• Quicker response after exposure -> Peak rises after fewer days + more sharply
• Higher peak height
Remember to revise antibody graphs for primary and secondary immune response.
See diagram pg 45 of revision guide.
What is vaccination?
The introduction of a specific disease antigen into the body in order to stimulate an immune response against a particular disease.
How does a vaccine work?
- Antigens (or dead pathogens) for a particular disease are injected into a human
- This prompts the primary immune response.
- Memory cells are produced.
- These allow a faster response next time an infection occurs -> Antibodies produced quicker.
What is herd immunity?
When a large percentage of the population is vaccinated, the rest of the population is also less likely to catch the disease since there are fewer people to catch it from.
What are the two ways a vaccine can be done?
- Orally
* Injection
What is the disadvantage of taking a vaccine orally?
It may be broken down by enzymes in the gut or the molecules of the vaccine may be too large to be absorbed into the blood.
Why are booster vaccinations given?
To boost the levels of memory cells.
How may the antigens in a vaccine be made harmless?
- Free antigens
- Dead pathogen
- Weakened pathogen