3.2.4 Immunity (C5) Flashcards
What is immunity?
When the body’s defences are able to kill a pathogen before it can cause harm.
What is an antigen?
A (glyco)protein on the surface of a cell membrane.
That (in the case of a foreign antigen) will trigger an immune response.
Describe non-specific defences.
General
Immediate
Identify the 2 types of white blood cell.
- T - Cells (Helper or Cytotoxic)
- B - Cells (Memory and Plasma)
How is the immune response controlled in organ transplant patients to prevent organ rejection?
Immunosupressant drugs
Organs donated by family members - for a close tissue match.
Why is there a time lag between infection and an immune response?
Clonal selection takes time i.e. the correct T/B Cell binding to the non self antigen.
Antigens that belong to the body have _____ antigens on their cell membrane.
SELF
When can the immune system cause problems for medical patients?
People who have received organ transplants.
The transplanted organs have non self antigens.
The immune system will destroy the non self material.
Foregn antigens are usually found on which 4 materials that can trigger an immune response?
- Pathogens
- Cells from other or the same species (organ transplants)
- Toxins from pathogens
- Cancer cells
Describe specific defences
Less rapid
Long lasting
Highly specific
Identify the non-specific defences against infection.
- S.T.E.M.S (Skin, Tears, Earwax, Mucus, Stomach Acid)
- Pagocytosis
Antigens can be which biological molecules?
Proteins (glycoproteins)
Lipids (glycolipids)
What is it about proteins that makes them useful as antigens?
Their specific 3D structure can form a variety of different ‘labels’.
Antigens that do not belong to the body have _____ antigens on their cell membrane.
NON SELF
What is a pathogen?
A microorganism that causes infectious disease.
What is meant by a SELF antigen?
A glycoprotein or glycolipid found on a cell surface membrane of a cell that belongs to the organism.
What is meant by a NON-SELF antigen?
A glycoprotein or glycolipid found on a cell surface membrane of a cell that does not belong to the organism.
How do phagocytes protect against pathogens, toxins, cancer cells or foreign tissues?
Phagocyte recognizes antigen
Pathogen is engulfed into a phagosome
Lysosome fuses with phagosome forming a phagolysosome
Lysozyme (hydrolitic enzymes) hydrolyse pathogen
Antigens from pathogen may be presented on the surface of the cell
What is phagocytosis?
When foreign material is ingested by a phagocyte to form a phagosome.
T-Cells can be one of 2 types. What are they?
Helper T-Cells
Cytotoxic T-Cells
Identify the 2 types of white blood cell.
Phagocytes
Lymphocytes (B cells and T cells)
What are lysozymes?
Hydrolytic enzymes found inside lysosomes that digest foreign material.
What is a phagosome?
A vesicle containing foreign material within a phagocyte that is formed during phagocytosis.
Is phagocytosis a specific or a non-specific response to a non-self antigen?
Non-specific
Are Phagocytes ‘antigen presenting cells’?
Yes - they present foreign antigens on their surface after engulfing a foreign material.
Describe how phagocytosis of a virus leads to presentation of its antigens
Phagosome FUSES with lysosome
lysosome contains lyzozymes which destroy virus]
antigen displayed on cell MEMBRANE of phagocyte (APC)
Which type of immunity are T-Cells mainly involved in?
Cell Mediated Immunity (they are just used to stimulate B-cells in humoural immunity)
Where can non-self antigens be found that T-Cells may bind to?
- The surface of an antigen presenting cell (phagocyte)
- Body cells invaded by a virus may present viral antigens.
- Transplanted cells from organ donors.
- Cancer cells
- Toxins produced by pathogens.
Can T-Cells bind to non-self antigens floating around freely in the blood?
No - they can only bind to foreign antigens that have been presented on an antigen presenting cell e.g. phagocyte.
How do cytotoxic T Cells (Tc) protect against disease?
They kill cells infected by pathogens or cancerous cells.
They produce a protein called perforin.
Perforin creates holes in target cell membranes, which kills the cell.
Where do T-Cells mature?
In the thymus
Where are all lymphocytes produced?
Bone marrow
Where do B-Lymphocytes mature?
In the bone marrow.
What is meant by cell mediated immunity?
An immune response that does not involve the production of antibodies.
Results in the production of cytotoxic T cells that can protect against pathogens.
Describe the process of cell mediated immunity (immunity that does not result in the production of antibodies).
- Phagocytosis of foreign material by phagocyte.
- Foreign antigens from material are presented on phagocyte.
- Specific T-helper lymphocyte (Th) binds to foreign antigen (clonal selection)
- Attachment causes Th cell to undergo mitosis (clonal expansion).
- Cloned T cells can:
- become memory cells for rapid future response.to same pathogen.
- stimulate phagocytes to engulf via phagocytosis.
- stimulate B cells to divide and release antibodies (humoural response)
- activate cytotoxic T cells (Tc) cells to kill.
What can the cloned T-lymphocytes do after clonal expansion has taken place in the cell mediated response?
- become memory cells for rapid future response.to same pathogen.
- stimulate phagocytes to engulf via phagocytosis.
- stimulate B cells to divide and release antibodies (humoural response)
- activate cytotoxic T cells (Tc) cells to kill.
what is an antibody?
Protein specific to an antigen
produced by B cells/secreted by plasma cells
What is meant by ‘humoral immunity’?
An immune response that involves the destruction of pathogens using antibodies.
How many different types of B-lymphocytes exist in the body?
Plasma cells
Memory cells
Plasma cells develop from B-lymphocytes. What is their function?
They produce antibodies to destroy pathogens.
Memory cells can develop from B-lymphocytes. What is their function?
They are responsible for the secondary immune response.
If they encounter the same pathogen again they multiply rapidly and develop into plasma cells, which produce antibodies.
Describe the process of humoral immunity.
- Foreign antigen enters blood, initiating an immune response.
- A specific B-lymphocyte engulfs forein antigen via endocytosis and presents foreign antigens on its cell surface membrane.
- Th cell binds to and stimulates specfic B-lymphocyte to undergo mitosis (clonal selection).
- Cloned B-lymphocytes develop into plasma cells that produce monoclonal antibodies (primary response).
- Some B-lymphocytes become memory cells that circulate blood ready to develop into plasma cells upon a recurring infection (secondary response).
Describe how the presentation of a viral antigen leads to the secretion of antibody against viral antigens
T cells bind to the antigen (on APC)
T cells are activated in to T helper cells
T helper cells stimulate SPECIFIC B cells
B cells stimulated to divide by mitosis (clonal selection)
Forms plasma cells which release antibodies
What makes all antibodies unique?
Secondary is
FASTER
GREATER concentration in antibodies produced
No LAG/Delay in antibody production
How is passive immunity different to active immunity
Passive is
QUICKER
No MEMORY cells produced
Draw and Label and antibody
How many polypeptide chains make up an antibody?
4
What does the antibody binding site bind to?
A complementary antigen
What do we call an antibody that is bound to an antigen?
An antigen-antibody complex
How does an antibody lead to the destruction of an antigen?
- They cause agglutination of bacterial cells - clumping together to make it easier for a phagocyte to locate them.
- They serve as markers that stimulate phagocytes to engulf the bacterial cells to which they’re attached.
What is agglutination and how is it possible?
When an antibody binds to bacterial cells and causes them to clump together.
It is possible because antigens have 2 binding sites
Describe how monoclonal antibodies be used to treat cancer?
- produce monoclonal antibodies specific to the antigen on the cancer cell.
- give these to a patient and they will attach to the cancer cells.
- They will block the chemical signals that stimulate uncontrolled growth of cancer cells
Why are monoclonal antibodies better treatment in some cases than drugs?
Fewer side effects due to a very specific responce on target cells.
Radioactive or cytotoxic drugs can be attached to monoclonal antibodies. How do these kill cancer cells?
The antibody with the attached drug attaches specifically to the cancer cell, and the drug kills the cell in a very targetted way.
Monoclonal antibodies are used to test for HIV. What is the name of this test?
ELISA test
What are the ethical issue related to the use of monoclonal antibodies?
- Mice are used to produce both tumour cells and monoclonal antiibodies. The use of animals in medical research nad treatment is an ethical issue as welfare is in quesiton.
- Although the use of monoclonal antibiodies saves many lives, there have been some deaths associated with their use (i.e. in the treatment of MS). It is important that patients are made fully aware of any potential risks.
- Accidents in medical trials involving human volunteers in which poeple are harmed cause a lack or truth in in industry and processes.
Describe Humoral Immunity
T helper cells bind to the complimentary antigens presented by the specific B cell. Clonal selection.
T helper cells activate specific B cells.
The B cells rapidly divide by mitosis to produce plasma and memory B cells. This is clonal expansion.
These cloned plasma cells produce specific complementary antibodies to the antigens on the pathogen
Antibodies destroy the pathogen
How does the ELISA test work?
B. 1st mobile antibody complementary to the antigen of interest + coloured dye attached
C. 2nd antibody complementory to antigen immoblised in test strip
D. 3rd antibody immoblised + complemenmtary to 1st antibody
what does a vaccine contain?
dead/weakened pathogen
How does a vaccine lead to the production of antibodies?
- vaccine contains antigens from pathogen
- macrophage presents it on its surface
- T cell with complementary receptor binds
- activates T helper cells
- which activate specific B cells
- B cells selected, divide mitosis
- B cell divides into plasma cells producing antibodies
difference between passive and active immunity
- active involves memory cells (passive doesn’t)
- active produces antibodies from plasma cells
- passive antibodies come from another source (breast milk)
- Active provides long term immunity
- Passive short term immunity - antibodies don’t last forever
- Active slower acting, passive fast acting
does a vaccination lead to active or passive immunity?
Active, as it leads to antibody production.
does a vaccination lead to artificial or natural active immunity?
artificial
what differs between the antibody production during a vaccination / primary infection, and secondary infection?
on secondary infection there are more antibodies produced, the production is more rapid, and they remain in the blood for longer.
is a vaccination a preventative measure or a cure for a contagious disease?
preventative, if someone already has the disease a vaccine is useless.
what are the features of a successful vaccination program?
- must be economically viable to make the vaccine on a large scale.
- there must be few side effects as uptake will fall.
- must be easy to produce, store and transport (this may require refrigerated vehicles).
- must be easily administered by trained staff
- must be able to vaccinate a large proportion of the population.
What is meant by the term ‘herd immunity’?
When a large proportion of the population have been vaccinated and are as a result immune to a disease. This means that those who are unvaccinated or susceptible to the disease are less likely to be in contact with each other so it is unlikely that the disease will spread.
Which members of a population are expected to be most susceptible to disease?
- babies and very young children who have not yet been vaccinated.
- those with compromised immune systems
Why does vaccination rarely eradicate diseases?
- immunity is not induced in those with defective immune systems.
- it is still possible to catch the disease immediately after vaccination as immunity has not yet been achieved.
- Pathogens may mutate so antigens change (e.g. antigenic variability in the influenza virus).
- there may be many strains of a particular disease (e.g. the common cold).
- some pathogens hide from the immune system (e.g. cholera).
- People refuse to get themselves and their children vaccinated.
Why might some people have ethical objections to vaccination programs?
- they are tested on animals
- they may have side effects
- can individuals be forced to get vaccinated in the interest of public health?
- is it acceptable to trial a new vaccine in a country where the disease is the most common?
- is it right to make vaccination compulsory regardless of personal belief?
- should we continue to use expensive vaccines if the cases of a disease are very low or kill very few?
What is antigenic variability?
The antigens on a pathogen (e.g. virus) mutate and change
Why is it difficult to make a vaccine against HIV?
The antigens mutate frequently and become unrecognisable to the immune system (antigenic variability)
What is a monoclonal antibody?
An antibody produced by a single clone of a B cell
Give some uses of monoclonal antibodies.
- targeting medication to specific cell types
- medical diagnosis
- pregnancy testing
