Immunity Flashcards
Define immunity
the means by which the body protects itself from infection
Outline a non specific defence mechanism
Immediate response
Same for all pathogens
Physical barriers and phagocytosis
Outline a specific defence mechanism
Slower response
Specific to each pathogen
Cell mediated response and humoral responce
Name 3 physical barriers
Skin Mucus Ear wax Hair Tears Stomach Acid Scabbing
Why does the body’s immune system take a number of days to control an infection?
Lymphocytes must build up their numbers/replicate
And this takes a long time
Why is it incorrect to say the body takes several days to respond to infection?
The body responds immediately by recognising foreign antigens
And carrying out phagocytosis
Briefly outline phagocytosis
- Phagocyte identifies pathogen
- Receptors bind to pathogen
- Pathogen trapped in phagosome
- Lysosomes fuse with phagosome
- Pathogen is hydrolysed
- Antigen is displayed of phagosome cell surface
How are pathogens destroyed in phagocytosis
Lysosomes containing enzymes
Lysozymes
Hydrolyse the pathogen
Why might phagocytes be abundant in tears?
Protective covering of the eye and tear ducts are pathogen entry points
Tears hydrolyse pathogens that try to enter through the eye
Before infection and harm can occur
Define antigen
A molecule from the cell surface membrane
That triggers an immune response
By lymphocytes
What are the two types of lymphocyte?
B lymphocytes
T lympohcytes
Briefly outline cell-mediated immunity
- Receptors on Th cells fit onto antigens displayed on phagocytes cell surface
- Th cell activates
- Th cell rapidly divides by mitosis to form clones
What can a clones T helper cell do?
Develop into a memory cell
Stimulate phagocytes to perform phagocytosis
Stimulate B cells to divide
Activate Tc Cells
How does a cytotoxic T cell kill infected cells?
Produces a protein; Perforin
That makes holes in the cell surface membrane
Allowing free movement of substances
Destroying the cell
Which type of pathogen are Tc cells most effective against?
Virsuses
They use living cells to replicate
Name 2 similarities between T cells and B cells
Both white blood cells Both lymphocytes Both have a role in immunity Both produced from stem cells Both produce memory cells
Name 2 differences between T cells and B cells
Mature in: T cells = thyumus gland, B cell = bone marrow
T Cell = cell-mediated immunity, B cell = homural immunity
T Cells cant produce antibodies, B cells can
T Cells only detect presented antigens, B cells detect any antigens
Briefly outline humoral immunity
- B cells take up and process antigens
- Th cells activate the B cell
- The B cell rapidly divides by mitosis to form clones
What can cloned B cells do?
Become plasma cells
Become memory cells
What does a plasma cell do?
Produces antibodies
Only survive a few days
Produce 2000 antibodies a second
What does a memory cell do?
Survive for up to decades
Rapidly divide into new T cells and B cells when they encounter a specific antigen
Providing long term immunity
Why is a secondary immune response more rapid than a primary immune response?
Antigens have not been ingested, processed or presented in a primary response
The immune response takes time as these steps must occur consecutively
In a secondary response memory cells are present and only require cloning and development into plasma cells
Fewer processes mean a quicker response
Outline 2 differences between Cell-mediated immunity and humoral immunity
Cell-mediated = T cells, Humoral = B cells
Cell mediated = no antibodies, Humoral = antibodies
Cell mediated = effective through cells, humoral = efffective through body fluid
Outline 2 similarities between Cell-mediated immunity and humoral immunity
Both immune responses
Both specific immune responses
Both produce memory cells
Both require antigens
Define antibody
A protein produced by lymphocytes in response to the presence of an appropriate antigen
Outline the structure of an antibody
Four polypeptide chains; 2 heavy chains, 2 light chains
Binding site that is complimentary to specific antigen
Variable region that results in different binding site shapes
Constant region that binds to receptors on cells (eg b cells)
How does an antibody lead to the destruction of an antigen?
Agglutination; clumps bacterial cells together for easier location by phagocytes
Serve as markers to stimulate phagocytosis
Define monoclonal antibody
An antibody produced by a single clone of cells
How can antibodies be used in medicine?
Targeting cancer cells
Diagnosis of diseases
Pregnancy testing
Name 2 ethical pros of using antibodies in medicine
Treat life threatening diseases such as cancer
Diagnose life threatening diseases
Rapid results
More effective than other methods of treatment
Name 2 ethical cons of using antibodies in medicine
Involves use of mice by giving mice cancer
Has resulted in some deaths; multiple sclerosis
Trial tests in March 2006 resulted in all volunteers suffering multiple organ failure
Define passive immunity
resistance to disease that is acquired from the introduction of antibodies from another individual rather than your own immune system
Define active immunity
resistance to disease resulting from the activities of an individuals own immune system whereby an antigen induces plasma cells to produce antibodies
What is the difference between natural active immunity and artificial active immunity
Natural results from an individual becoming infected and producing its own antibodies
Artificial comes from vaccination and results in the production of antibodies due to exposure to the antigen, but no infection
What signs must a vaccination show to be successful?
Economically beneficial Few side effects Easily produced, transported and stored Means of administration available Majority of vulnerable population must be vaccinated
Define her immunity
Majority of the population is vaccinated
So pathogen is difficult to spread
Protecting susceptible individuals
Why might a vaccination not eliminate a disease?
Vaccination fails to induce immunity Infection immediately after vaccination Frequent mutation of the pathogen Too many varieties of the pathogen Pathogens hiding in body cells Objections of vaccination (eg religion)
Define antigenic variablity
A change in a pathogens antigens resulting in the immune system no long producing antibodies to destroy the pathogen
Name 3 ethical questions that should be taken into account with vaccination
How acceptable is vaccine production?
How can side-effects be balanced against the risk of infection?
Who should vaccines be tested on?
Should vaccines be compulsory?
Should vaccination continue when the disease is almost eradicated?
Should vaccines with unknown side effects be issued in emergency situations?
What does HIV stand for?
Human immunodeficiency virus
What does AIDS stand for?
Acquired Immune deficiency syndrome
Outline the structure of HIV
Lipid envelope on outside With attachment proteins embedded Capsid inside protein layer Two strands of RNA inside capsid Reverse transcriptase inside capsid
How does HIV replicate?
- HIV enters blood stream and circulates body
- HIV binds to helper t cells
- Capsid fuses with cell surface membrane and contents of HIV enter cell
- HIV reverse transcriptase converts RNA into DNA
- New DNA inserts into cell’s DNA
- Messenger RNA creates new viral proteins and RNA
- HIV is pieced together and burst from the cell
How does HIV cause AIDS?
HIV attacks T helper cells
Reducing the number of T helper cells
So B cells cannot be stimulated
Resulting in a lack of adequate humoral response
What does ELISA stand for?
Enzyme linked immunosorbant assay
Outline the ELISA test
- Antigens attach to a surface
- Wash to remove unattached antigens
- Add antibody specific to antigen so they bind
- Wash to remove excess antibody
- Add second antibody to bind with first antibody with attached enzyme
- Add colourless substrate of enzyme
- Enzyme hydrolyses substance if present, giving a coloured positive result
