Chapter 5 Flashcards
What is infection caused by?
Pathogens
Explain the specific bodily responses to pathogens
Caused by lymphocytes and can be cell mediated or humoral
Cell mediated used T lymphocytes (Th cells and T cytotoxic cells)
Humoral uses B lymphocytes (B cells, memory cells, plasma cells)
Explain the non specific bodily responses to pathogens
Can have physical barriers: skin mucus HCl hair tears and ear wax
Can have response from phagocytes only able to identify between self and non self
Cells are identifiable by ____ in the cell surface membrane. The body is able to identify between cells that are —- and ——-
Antigens
Self
Non self
How do lymphocytes recognise cells belonging to the body?
In the fetus the lymphocytes are constantly colliding with other cells
Infection in the fetus is rare because it is protected by the placenta
Lymphocytes therefore only collide with self material
These lymphocytes either die or are repressed
The only remaining lymphocytes are ones that are specific to foreign material
In adults lymphocytes are produced in bone marrow and only encounter self antigens
Any lymphocytes that show an immune response to self undergo programmed apoptosis
No clones of these are made so the only lymphocytes present are those that respond to nonself material
The immune system can identify :
Pathogens
Non self material
Toxins
Abnormal body cells
All of which are potentially harmful and identifying them is the first step to removing the threat they pose
Explain the issue of transplants and how to overcome this
The immune system recognises transplants as foreign material and attempts to destroy the transplant
To minimise this response the donor tissues are matched as closely as possible to the tissues of the recipient and immunosuppressive drugs are often used to reduce the effect of the immune response
What is the primary response?
The activation of the immune system when an antigen enters the body for the first timw
The primary response can be described as —- and —-
Why?
Slow and small
Because there arent many B cells that can make antibodies needed to bind to it
After being exposed to the foreign antigen both T cells and B cells produce —— cells
What do these do
Memory
They remain in the body and recognise the specific antigen the next time it enters the body
What do memory B cells do?
They retain the ability to produce the specific antibody needed to bind to the antigen
What is the secondary immune response and why is it faster?
An immune response produced when a known pathogen enters the body again
It is faster and stronger because the memory B cells divide into plasma cells that produce the specific antibody to match the antigen
Memory T cells divide into the right type of T cells to kill the cell carrying the antigen
What are memory T cells?
Cells that retain the ability to divide into the specific type of T cell required to kill a specific cell carrying the antigen they are specific to
What is phagocytosis?
A mechanism by which cells engulf particles to form a vesicle or vacuole
Explain the process if phagocytosis
- Chemical products of pathogens or dead,damaged or abnormal cells act as attractants causing phagocytes to move towards the pathogen
- The receptors on their cell surface membrane recognise and attach to the chemicals on the surface of the pathogen
- They engulf the pathogen to form a vesicle known as a phagosome
- Lysosomes move toward the vesicles and fuse with it, the lysozymes present destroy the ingested bacteria by hydrolysis
What is a lysosome?
An organelle containing lysozmes enclosed in their membrane
What are lysozymes?
An enzyme which catalyses the hydrolysis of cells walls of certain bacteria
What are neutrophils?
White blood cells that engulf whole pathogens
What are macrophages?
White blood cells that engulf whole pathogens and retain proteins to present of their outer cell surface (antigen presenting cells) that stimulate a specific immune response
Binding + substance —->
shape change
Foreign antigens presented by phagocytosis bind to specific receptors on the cell surface of what cells?
What does this activate the response of?
T lymphocyte cells. T Helper Cells
What do T helper cells activate?
Phagocytes, T cytotoxic cells and B cells
What are T helper cells activated by?
Phagocytes
What are T cytotoxic cells?
cells that release toxins that bind to and kill foreign and abnormal cells in the body
What happens when a specific B cell is activated?
They divide via mitosis into identical cells called plasma cells. This is called clonal expansion.
What do plasma cells do?
They create antibodies to fight against specific antigems
How are B cells activated? What is the process called?
The specific antibody on the B cell binds to a specific foreign antigen. Clonal selection
Define agglutination
Something that clumps pathogens together. These pathogens are then engulfed by phagocytes and are destroyed.
Define antigen
a molecule that triggers an immune response by lymphocytes
define lymphocytes
types of white blood cells responsible for the immune response.
How are lymphocytes activates
By the presence of antigens
What are the 2 types of lymphocytes?
B lymphocytes which are associated with humoral immunity and T lymphocytes which are associated with cell-mediated immunity.
What is cell mediated immunity and which lymphocyte is associated with it?
An immune response which doesn’t involve antibodies
T lymphocytes
What is humoral immunity and which lymphocyte is associated with it?
An immune response involving antibodies found in bodily fluids. B lymphocytes
What are antigen presenting cells?
cells that present foreign antigens on their surface.
What are antigens made of and where do they come from?
antigens are usually proteins and are part of the cell-surface membrane of foreign cells
what do lymphocytes respond to?
Cells that have been infected by non-self material.
Why can T lymphocyte cells distinguish between invader cells and normal cells?
- Phagocytes that have engulfed pathogens present their antigens on their cell-surface membrane.
- Body cells invaded by a virus present some of the foreign antigens on their cell-surface membrane
- transplanted cells have different antigens
- cancer cells are different from normal body cells and present antigens on their cell-surface membrane.
Explain what a T cell can become or activate after it has been cloned via mitosis
- could become a memory cell that circulates in blood and tissue to respond to future infection
- stimulates B cells to divide
- stimulates phagocytosis by activating phagocytes
- Activates cytotoxic T cells that kill infected cells by using toxins to make holes in their cell membranes
Each receptor on a T cell responds to a _____ _____
a single antigen
Explain the stages of the T lymphocyte response
- Pathogens invade body cells or are taken in by phagocytes
- The phagocytes places the antigen from the pathogen on its cell-surface membrane
- Receptors on the helper T cells fit exactly to these antigens
- This attachment activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells
- The cloned cells follow one of the 4 possible outcomes they can follow.
What is the name of the toxin that cytotoxic T cells produce and what does it do to infected or damaged cells?
protein called perforin
makes holes in the cell surface membrane
makes cell membrane freely permeable and cells burst
Explain the process of how B cells produce complementary antibodies to specific antigens
- The surface antigens on invading pathogens are taken in by B cells and processed to be presented on its surface
- helper T cells attach to the processed antigens on the B cells and activates the B cell
- The B cell divides by mitosis to make clones of plasma cells
- These plasma cells produce and secrete the specific antibody that exactly fits the antigen on the pathogen’s surface
- The antibody attaches to the pathogen and destroys it
- Some B cells develop memory cells that can respond to future infections of the same pathogen by dividing rapidly and developing into plasma cells that produce antibodies
What do plasma cells do?
They secrete antibodies that lead to the destruction of the antigen.
What is the primary immune response?
The response of the body when it comes into contact with a new pathogen, usually involving the production of antibodies and memory cells
What is the secondary immune response?
The response of the body when it comes into contact with a pathogen it has already come into contact with, which involves mitosis of memory cells to make the same antibodies as before.
What is an antibody?
A blood protein produced in response to and counteracting a specific antigen
What are antibodies made by?
B cells
Explain the structure of antibodies
They have 2 identical bonding sites which are complementary to a specific antigen. They are made of 4 polypeptide chains in 2 pairs : heavy and light chains. The bonding site is known as the variable region and the rest is known as the constant region
What is the variable region on an antibody?
The bonding sites which are different on each antibody because they are specific to specific antigens
How does an antibody destroy a bacterial antigen?
Antibodies dont destroy antigens directly - they prepare them for destruction.
They cause agglutination of the bacterial cells so that phagocytes can locate them more easily and they serve as markers to stimulate phagocytosis.
Define monoclonal antibodies
antibodies than are produced by a single clone of cells (single type of antibody that can be isolated and cloned.
What are the advantages of monoclonal antibodies?
They are: cheap nontoxic highly specific used in small doses
and they have few side effects
Explain 2 uses of monoclonal antibodies
They can be used for medical diagnosis because by having an antigen react with the specific antibody it is possible to measure the level of antigen in the blood.
they can be used for pregnancy testing as hCG (hormone in early pregnancy) binds to the an antibody which then binds to another antibody which releases a coloured dye.
Explain the process of direct monoclonal antibody therapy
monoclonal antibodies are produced and are given to a patient. the antibodies attach themselves to receptors on cancer cells and block the chemical signals that stimulate the uncontrolled growth
Explain the process of indirect monoclonal antibody therapy
involves attaching a radioactive substance or cytotoxic drug to a monoclonal antibody which then attached to a cancer cell which is then killed by the substance
What are the ethical issues of monoclonal antibodies
involve animal use - cause cancer in mice
have lead to some deaths in patients with multiple sclerosis - informed consent
testing for safety of new drug presents certain dangers
Define immunity
The means by which the body protects itself from infection
Define vaccination
The introduction of the appropriate disease antigens into the body - either by mouth or by injection
Define herd immunity
immunity that arises when a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread within the population
List some ethical issues with vaccinations
Use animal testing
Can have long term side affects
How can they ethically trial the vaccine - who to use as a lab rat
Should vaccinations be compulsory
What if there are existing health risks and vaccinating would harm them, but if not vaccinated risks herd immunity,
Why doesn’t vaccination always eliminate disease?
vaccination doesnt always lead to immunity in a person
individuals may develop the disease directly after the vaccination - this can then spread
pathogenic mutation
too many varieties of pathogens to vaccinate agaist
Pathogens can hide from the immune system so it is never treated
individuals may choose not to be vaccinated due to ethics
List some features of a successful vaccination programme
must be economically available in large quantities
must have few non serious side effects
there must be means to produce, store and transport the vaccine
there must be ways to administer the vaccination
it must be possible to vaccinate the vast majority of the population
What does a successful vaccination programme require
Staff equipment training hygienic conditions centres of distribution refrigerated transport
Why does published scientific evidence need to be treated with caution?
can be biased by personal belief
interpretation by the media can be biased
new knowledge can challenge currently accepted ideology
universal acceptance needs critical appraisal which can take time
scientists could be paid to present evidence in a certain way
How does HIV infect T helper cells?
- Glycoproteins on the surface of HIV bind to receptor proteins on the cell-surface membrane of T helper cells
- The capsid is released into the cytoplasm of the T helper cells.
- RNA and enzymes (reverse transcriptase and intergrase) are released from the capsid
- Reverse transcriptase changes single-stranded RNA into double-stranded DNA
- Intergrase inserts this DNA into the nucleus
- The genes in the HIV DNA are expressed instead of their own geenes
- HIV proteins are synthesised and new HIV RNA is made
- New HIV viruses are released from the T helper cell
- The T helper cell dies
- The HIV viruses infect new cells
List the features of a HIV virus
Attachment proteins RNA as genetic material Matric Liquid envelope capsid
How does HIV cause the symptoms of aids?
Too few T helper cells as they die when HIV leaves them
So B cells arent stimulated to produce antibodies and cytotoxic T cells are not stimulated to produce toxins
So there is no adequate immune response and the patient becomes susceptible to infections and cancers
What are the symptoms of AIDs
Flu like symptoms leading to fever and chills seen within 4 weeks
Can take up to 10 years to develop.
Why are antibiotics ineffective against viral diseases?
Antibodies dont destroy viruses because they target the murein in bacterial cell walls which means when water enters the cell instead of becoming turgid the cell bursts and the bacteria dies. Because viruses use host cells to carry out metabolic activities they dont have a cell wall to target without affecting the host cells.
What kind of drugs could be used to target viruses in the future?
Drugs targeting reverse transcriptase as human cells dont have this and it would prevent the cells from being used as host cells.
Explain what the ELISA test does
It uses antibodies to detect the presence and quantity of a protein in a sample
Summarise the method of the ELISA test
- Apply sample to a surface for the antigens to attach to
- Wash the surface to remove unattached antigens
- Add the antibody that is specific to the antigen
- Wash the surface to remove unattached antibodies
- Add a second antibody that binds to the first - this will have a receptor enzyme attached
- Add colourless substrate of the enzyme so the receptor changes colour
- The amount of antigen present can be shown by the intensity of the colour produced.
