2C Cells and the Immune System Flashcards
Why is HIV so deadly?
The body cannot detect it as it is in our body cells
What is an antigen?
Any part of an organism (often proteins found on the surface) that is recognised and foreign by our immune system
What are antigens controlled by?
Genes
Why are organ transplants usually taken from family members?
Antigens are genetically controlled therefore your family will have similar antigens, making it less likely for the organ to be rejected
How many immune systems are there in our bodies?
2
What are the two immune systems in our bodies called?
- -> Non-specific
- -> Specific
Which immune system do all animals have?
Non-specific
Which immune system do only vertebrates have?
Specific
What is the nonspecific immune system like?
- Immediate response
- Physical barriers
- Phagocytosis (as this is the same for all responses)
What is the specific immune system like?
- Slower response
- B and T lymphocytes
Name 3 barriers to infection
- Skin
- Hydrochloric acid
- Epithelial mucus
How does the skin protect our body from infection?
Pathogens find it difficult to penetrate
How does HCL protect our body from infection?
Denatures enzymes or coat proteins of most pathogens
How does Epithelial mucus protect our body from infection?
Epithelial layers inside the body produce mucus that pathogens stick to + become immobilised
What is a Phagosome?
Where the pathogen in broken down in a phagocyte, the pathogen is transported by vesicles
What is a Lysozyme?
Enzymes found in Lysosomes
Why are T lymphocytes called T lymphocytes?
They mature in the Thymus gland
What is cell mediated immunity?
The pathogen must be present for T lymphocytes to be made
How do T lymphocytes identify specific antigens?
They have receptor proteins on each cell that can detect one specific antigen
How many different types of T cells are there?
10^8 - each of these display different receptors
What are the two forms of T cells?
- Helper T cells (Th cells)
- Cytotoxic T cells (Tc cells)
What is an antigen presenting cell?
A cell that presents antigens on its surface
Which cells have antigens on the surface?
- Cancerous cells
- non-self cells
What happens after a phagocyte has destroyed the pathogen?
The phagocyte present the antigens on their outer membrane
What is the role of a Tc cell?
- Produces the perforin protein
- Make holes in cell surface membrane
- Results in cell death
What are the 4 things activated T cells can do?
- Divide via mitosis to produce Th cell clones
- Release cytokines to activate Tc cells
- Activate B cells
- Stimulate phagocytosis
What do receptors on T cells bind to?
Antigens on antigen-presenting cells
What is humoral immunity?
- Involves antibodies
- Specific immune response
- B cells
What are B cells?
A type of white blood cell
Covered with antibodies which bind antigens to form an antigen-antibody complex
Which type of cells are involved in humoral immunity?
B cells
Which type of cells are involved in cell mediated immunity?
T cells
B lymphocytes are also known as what
B cells
What are the first 4 stages of humoral immunity?
1 - B cell with complementary antibody engulfs pathogen
2 - B cell presents antigen
3 - Th cell binds to the presented antigen using its complementary receptor protein
4 - Activates B cell to divide
What is the primary response in humoral immunity?
5 - Plasma cell clones made to secrete antibodies
6 - Attach to antigens and:
- agglutinate (stick to target)
- Stop pathogens invading body cell
- Bind to free toxin proteinsWhat is the secondary response in humoral immunity?
7 - Memory cells made, circulate in the blood for future infections
Active immunity = ?
immoral imunity
What is the structure of an antibody?
Composed of 4 polypeptide chains and makes a y shaped structure
What are the polypeptide chains in antibodies like?
There are 4:
- 2 light
- 2 heavy
What are the polypeptide chains in antibodies joined by?
Disulfide bonds
Describe the Y shaped structure of an antibody
- The stem = constant region
- End of arms = variable regions that bind to the antigen
What is a monoclonal antibody?
Antibodies produced from a single group of genetically identical B cells (plasma cells) specific to one type of antigen
Why are the B cells in monoclonal antibodies genetically identical?
- They have the same primary structure as they are coded by the same genes
- As a result have the same secondary + tertiary structure
How are monoclonal antibodies produce (3 stages)?
FINISH WRITING THIS FROM TEXTBOOK
- The specific antigen binds to the receptor on the B cell
2. A helper T cell sends out a chemical signal to activate the B cell which then releases specific
Which animal do we use to produce antibodies for monoclonal antibodies?
Mice - they are small but produce the right antibodies
What makes it easier to produce monoclonal antibodies to bind to specific molecules?
- They all have the same tertiary structure
- They therefore all bind to a specific antigen with a complementary shape
What are the unique antigens on cancer cells called?
Tumor markers
What are the drugs called that can be used to bind to the tumor markers on cancer cells?
Anticancer drugs
Why are the side effects reduced from anticancer drugs?
- The drugs will only accumulate at specific cells
- The drugs will only be released where antibody binding occurs
What hormone is produced when a woman is pregnant and can be detected in their urine?
hCG
Explain how a pregnancy test works.
- The hormone hCG is released in a pregnant woman’s urine
- Monoclonal antibodies are immobilised in coloured beads on a test strip
- When urine is applied hCG will attach to antibodies to form an antigen-antibody-colour complex
- hCG antigen-antibody-colour complex moves along the strip until it is trapped by a different antibody
- Complex accumulates to produce a line - confirms pregnancy
What is an ethical issue of using mice to produce antibodies?
You are giving cancer to mice, effectively killing them
What is an ethical issue with drug trials?
They’re not always safe - one trial, within 6 minutes 6 participants went into multiple organ failure despite all previous testing showing no signs of damage
What are the 5 stages of cell-mediated immunity?
1 - Pathogens invade body cells or are taken on by phagocytes
2 - The phagocyte places antigens from the pathogen on its cell-surface membrane
3 - Receptors on a specific helper T cell (Th cell) fit exactly onto these antigens
4 - This attachment activates the T cell to divide rapidly via mitosis + form a clone of genetically identical cells
5 - There are cloned T cells which have individual roles
In the 5th stage of cell mediated immunity, what are the 4 roles the cloned T cells can have?
- Develop into memory cells (enable rapid response to future infections by the same pathogen)
- Stimulate phagocytes to engulf pathogens via phagocytosis
- Stimulate B cells to divide + secrete their antibody
- Activate cytotoxic T cells (Tc cells)
When does the primary immune response happen?
When new pathogens first invade the body
During the primary response, how many initial specific T and B cells are there?
Very few, there are also relatively few clones produced
During which response are symptoms visible?
Primary
During which response are symptoms not visible?
Secondary
When does the person become ‘immune’ from the primary response?
When the infection has been detected and responded to
Which type of cells differentiate into memory cells?
Activated B cells and Th cells
How long can memory cells stay in to blood?
Many years
When does the secondary response happen?
When the same pathogen infects again
How does the secondary response differ to the primary response?
The memory cells are already present in the secondary immune response so they can react much faster
What sort of cells are produced in a secondary response?
- Memory T cells divide into cytotoxic T cells
- B cells divide into plasma cells
Is a primary or secondary response stronger?
Secondary
Give one example of active immunity
Vaccination
What do vaccines contain?
Dead or weakened pathogens
How does a vaccine work?
They do not cause disease but do contain the antigens necessary to illicit a primary immune response
If the person becomes infected after having the specific vaccine for that, which response will occur?
Secondary
Give 2 examples of passive immunity
- Naturally –> mother to baby
- Artificially –> Injecting antibodies
How can someone become naturally immune?
The mother may have memory cells which get passed to the child
How can someone become artificially immune?
- Taken from the blood plasma
- The antibodies assist the body’s normal immune response
- Does not lead to long term immunity
What is the enzyme in HIV?
Reverse transcriptase
Why is HIV called a retrovirus?
It’s reverse transcribing
Are antibodies received in breast milk active or passive immunity?
Passive
Are antibodies made during reinfection active or passive immunity?
Passive
T cells can differentiate into…
- Helper cells
- Cytotoxic cells`
What is the reason why the flu vaccine has to change every year?
Antigenic variability
What is part of the specific immune system?
- -> Cell-mediated response
- -> Humoral response
B cells can differentiate into…
- Plasma cells
- Memory cells
T cells are associated with…
Cell mediated immunity
What is part of the nonspecific immune system?
- Physical barrier
- Phagocytosis
B cells are associated with..
Humoral immunity
Are vaccinations active or passive immunity?
Active
Describe what happens to the pathogen once it is engulfed into a vesicle by a phagocyte.
Vesicle fuses with phagosome, lysosomes release hydrolytic enzymes into phagosome to digest the pathogen.
Where is the enzyme reverse transcriptase found?
In retroviruses
What sort of cells can B cells differentiate into?
- Memory cells
- Plasma cells
What sort of cells can T cells differentiate into?
- Helper cells
- Cytotoxic cells
What is herd immunity?
If enough people are immune to a pathogen (>90%) then the remaining people are often protected
Why does herd immunity work?
Due to the lack of hosts for the pathogen to reproduce in
Give an example of antigenic variability
The flu
What is antigenic variability?
Pathogens develop new strains, with different antigens so the body does not have memory cells against them
What is antigenic variability caused by?
Mutations or horizontal transfer of plasmids containing new genes
What does infection by a new strain (in antigenic variability) mean?
The body has to perform the primary response again as the virus needs to be detected and responded to
How many stages are there in HIV replication?
8
What is the first stage in HIV replication?(after infection)
Following infection, HIV enters the bloodstream and circulates around the body
What is the second stage of HIV replication?(attach to cell)
A protein on the HIV readily binds to a protein called CD- this protein occurs on a number of cells, HIV mostly attaches to T helper cells
What is the third stage of HIV replication? (what does the capsid do)
The protein capsid fuses with the cell-surface membrane -RNA + enzymes of HIV enter the T helper cell
What is the fourth stage of HIV replication?(enzyme)
The HIV reverse transcriptase converts the virus’s RNA into DNA
What is the fifth stage of HIV replication?(nucleus)
The newly made DNA is moved into the T helper cell’s nucleus where it is inserted into the cell’s DNA
What is the sixth stage of HIV replication? (mRNA created)
The HIV DNA in the nucleus creates mRNA using the cell’s enzymes - the mRNA has instructions for making new viral proteins + the RNA to go into the new HIV
What is the seventh stage of HIV replication?(leaves nucleus)
The mRNA passes out of the nucleus through a nuclear pore and uses the cell’s protein synthesis mechanisms to make HIV particles
What is the eighth stage of HIV replication?(leaves cell)
The HIV particles break away from the helper T cell with a piece of its cell-surface membrane surrounding them which forms their lipid envelope
How many Th cells does a healthy person have in their bloodstream?
1000mm^3
How many Th cells do AIDs sufferers have in their bloodstream?
200mm^3
Does HIV/AIDs kill you?
Normally a cold or ill health associated with it does
How can HIV/AIDs be cured?
- -> no cure for HIV/AIDs
- -> Only treatment to prolong their life
What is the ELISA test used to detect?
- HIV
- Hepatitis
- TB
What can the ELISA test as well as HIV, TB and Hepatitis?
Can detect the amount of drugs in a person
How does the ELISA test work?
- Uses antibodies to detect presence + quantity of a protein
- Very sensitive so can detect the smallest amounts of a protein
What is the enzyme is the ELISA test linked to?
Immunosorbent assay
Give 3 reasons why antibiotics don’t work on viruses?
- No metabolic processes or cell structures for antibiotics to interrupt
- Working within own body cells
- Protein coat means that antibodies cannot bind to sites
What are the 5 stages of a pathogen’s response?
- A phagocyte recognises the foreign antigens on a pathogen
- Cytoplasm of the phagocyte moves round the pathogen, engulfing it
- The pathogen is now contained in the phagosome in the cytoplasm of the phagocyte
- A lysosome fuses to the phagosome and the lysozymes in the lysosome break down the pathogen
- The phagocyte presents the pathogen’s antigens - it sticks the antigens on its surface to activate other immune system cells
What is a phagocyte?
A type of white blood cell that carries out phagocytosis
Where are phagocytes found?
In the blood and tissues
They are the first cell to respond to an immune system trigger inside the body
Where are antigens?
Usually on the surface of cells
What are antigens used by the immune system for?
To identify:
- Pathogens
- Abnormal body cells
- Toxins
- Cells from other individuals of the same species
What are the 4 main stages in the immune response?
- Phagocytes engulf pathogens
- Phagocytes activate T-cells
- T-cells activate B-cells which divide into plasma cells
- Plasma cells make more antibodies to a specific antigen
What is a T-cell?
A type of white blood cell (also called a T-lymphocyte)
What do T-cells have on their surface and how does this affect their function?
It has receptor proteins on its surface that bind to complementary antigens presented to it my phagocytes
What do helper T-cells (Th cells) do?
They release chemical signals that activate & stimulate phagocytes
What do cytotoxic T-cells (Tc cells) do?
They kill abnormal and foreign cells
How are B-cells activated?
Th cells activate them
How are B-cells specific?
Each B-cell has a different shaped antibody on its membrane, so different B-cells bind to different shaped antigens
How do B-cells divide into plasma cells?
1) When the antibody on the surface of a B-cell meets a complementary shaped antigen, it binds to it
2) This, together with substances released from helper T-cells, activated the B-cell - this process is called Clonal Selection
3) The activated B-cell divides into plasma cells
What are plasma cells?
They are identical to B-cells (they’re clones)
They secrete loads of antibodies specific to the antigen - these are called monoclonal antibodies
What do antibodies produced by plasma cells do?
They bind to the the antigens on the surface of the pathogen to form lots of antigen-antibody complexes
How many bindings sites does an antibody have?
They have 2 binding sites, so they can bind two pathogens at the same time
What is agglutination?
Where pathogens become clumped together at the binding sites on an antibody
How do antibodies destroy pathogens?
Pathogens attach to the binding sites on the antibody. Agglutination occurs and phagocytes bind to the antibodies and phagocytose many pathogens at once
This process lead to the destruction of pathogens carrying this antigen in the body
What does the cell mediated response involve?
The T-cells and other immune system cells that they interact with eg phagocytes
What does the humoral response involve?
B-cells, clonal selection & the production of monoclonal antibodies form the humoral response
Why are both the cell mediated and humoral response needed?
The responses interact with each other to remove a pathogen from the body
e.g. T-cells help to activate B-cells, and antibodies coat pathogens making it easier for phagocytes to engulf them
How do vaccinations work?
Contain antigens for your body to produce memory cells without catching the disease
How do vaccination help people who don’t have one?
Herd immunity, fewer to catch it from
What are the pathogens like in vaccines?
Free or attached to a dead or weakened
How may vaccines been taken?
Injected or taken orally
What are the disadvantages or taking a vaccination orally?
Could be broken down by enzymes or molecules are to big to be absorbed
What is a booster vaccine?
Given later on, make sure memory cells are produced
How can pathogens evade the immune system?
Antigenic variation
What is antigenic variation?
When pathogens change the surface of their antigens, means when infected a second time memory cells wont recognise so primary response has to be carried out again
What is an example of an antigenic variation?
Influenza (flu)
