cell recognition and the immune system Flashcards
physical and chemical defense of the human body
first line of defense
skin, mucous, tears, saliva, inflammation, recognizing foreign cells to be targeted
how does the body recognise foreign cells
proteins on the surface of cells and viral particles allow them to be identified
often part of the phospholipid biolayer - glycolipids and proteins
function of proteins on the surface of cells
allows the body to recognise self and foreign cells
what types of cells are foreign
pathogenic cells
abnormal body cells
toxins
name of the molecule used by the body to identify foreign cells
antigen
examples of the importance of antigens
(phagocytosis)
phagocytes have surface proteins that act as receptors and bind to the proteins on the surface of pathogens
this means that pathogens can be ungulfed
the antigens that were in the pathogen can now be presented on the phagocyte
other cells of the immune system can then be recruited
ultimately what is the purpose of antigens
cell to cell recognition
self antigens definitiuon
antigens that are produced by the organisms own body cells
dont stimulate immune response
how do pathogens have antigen variability
antigens on their surface changes frequently due to genetic mutations
why is antigen variability bad
surface receptors on memory cells can only bind to one antigen so no secondary immune responses can form
role of phagocytes
recognise and engulf pathogens - phagocytosis
phagocytosis process
chemicals released by the pathogens attract phagocytes
phagocytes move toward the site of infection, non self antigens recognised
phagocyte binds to antigens on pathogen
cell membrane of phagocytes extends out entrapping the pathogen in the phagocytic vacuole
lysosome fuses with the phagocytic vacuole
hydrolytic enzymes digest the pathogen
pathogen us displayed on the cell surface
What type of cell are lymphocytes
White blood cell
Features of lymphocytes
Smaller than phagocytes
Large nucleus
Produced in the bone marrow
Life cycle of T - lymphocytes
Immature t lymphocytes form in the bone marrow
They leave the bone marrow to mature in the thymus
When they mature they develop T-cell receptors (basically an an antigen)
How do T cells divide
Mitosis
How do T-lymphocytes activate
When they encounter and bind to a specific antigen that is being presented by host cells
This could be a phagocyte
What happens when T lymphocytes activate
Divide by mitosis to increase in number
They then differentiate into :
Helper T cells
Cytotoxic T cells
What does an antigen presenting cell do
Present the antigens from toxins, ingested pathogens and foreign cells
Help to recruit other cells of the immune system
Specific immune response can be created
Many immune system cells can present antigens - examples
Macrophages and dendritic cells
Function of helper T cells
Assist other white blood cells in the immune response by releasing cytokines which stimulate :
Maturation of B lymphocytes into antibody secreting plasma cells
Production of memory B cells
Activation of cytotoxic T cells which destroy tumour cells
Killer T cells function
Patrol the body in search of antigen presenting cells
Attach to the foreign antigens on the cells membrane of infected cells
Secrete toxic substances that kill the infected body cells and the pathogen inside
What do B lymphocytes do
Mature the genes coding for antibodies
Once mature B lymphocyte cells make one type of antibody molecule - these remain on the cell surface membrane of the molecule
Part of each antibody forms a glycoprotein receptor that can combine specifically with one type of antigen
What must b cellss (when immature) do before developing antibody receptors
Divide by mitosis
Process of a primary immune response using B lymphocytes
Only one b cell has an antibody receptor that is specific to the shape of the antigen that has entered the body
The selected b cell divides by mitosis, some of the daughter cells develop into plasma cells others into memory cells
Plasma cells secrete antibodies that specifically combine with the antigen that has entered the body
What are antibodies
Globular glycoproteins
What protein level are antibodies (think how many chains they have)
Quaternary
What is the constant region of an antibody
Do not vary within a class but do vary between the classes of antibodies - constant region determines the mechanism used to destroy the pathogen
What is the variable region of an antibody
Change for every antibody
Also where the antigen binds to the antibody
What is the antigen binding site
At the end of every variable region, composed of around 120 amino acids
Varies greatly due to antibody specificity
What is the “hinge” region
Gives flexibility to the antibody molecule which allows the antigen binding site to be placed at different angles when binding
Its actually disulphide bridges
What are antigens a complementary to
Antibodies
What happens when an antigen collides with an antibody
It bonds together forming an antigen-antibody complex
How many antigen binding sites do antibodies have
2 - can bind to 2 at once this is called agglutination which groups lots of the pathogens together
What does agglutinations benefit means
Neutralises the pathogen and marks it to attract phagocytes to destroy the pathogen
What do B lymphocytes form during an immune response
Plasma and memory cells
What do memory cells do and secondary immune response
Create an immunological memory which lasts for years and when a pathogen is reencountered, the memory cells recognise the antigen and creates a after more effective response by dividing faster into plasma cells
What is the primary response
The initial B lymphocytes that divide by mitosis and become plasma cells (not the memory cells ones)
Secrete lots of antibodies which bind to antigens
Short lived
Slow reaction
Definition of a vaccine
A suspension of antigens that are intentionally put into the body to induce artificial active immunity
Live attuanated vaccine
With a weakened pathogen
Inactivated vaccine
Dead pathogen in
How do vaccines work
Produce long term immunity as they cause memory cells to be formed which when reencountering a pathogen produce a stronger secondary response
How are vaccines harmless
Do not cause the disease they protect against because the pathogen is killed by the primary immune response
Why may vaccines not be effective
Antigenic variation - there is variation in the antigen of pathogens so memory cells can’t store antibodies against it
What is antigenic concealment
Occurs when the pathogen hides from the immune system by living inside cells or when the pathogen coats their bodies in host proteins, so vaccines cannot recognise or remove the pathogen
Benefits of live attenuated and negatives
Pathogens multiply slowly so the primary response can destroy
Produce a longer and stronger response
Unsuitable if they have a weak immune system
benefits and negatives of inactivated vaccines
contain dead pathogens
cannot cause disease
do not trigger a strong or long lasting immune response
some may have allergic reactions to these vaccines
how does herd immunity arise
when a sufficently large amount of the population has been vaccinated
benifits and negatives of herd immunity
those that are not vaccinated are still protected as the pathogen is unable to spread
if vaccinations fall below the required level then herd immunity breaks down
reasons that eradicating disease can be difficult
pathogens are complex and vaccines cannot be developed for them
unstable political situation - hard to get vaccine out
lack of public health faci;ities
too few have been vaccinatied
what is active immunity
immunity aquired when an antigen enters the body triggering a specific immune response
naturally aquired when exposed to normal diseases or artificially aquired through vaccines
long term immunity
effective
what is natural passive immunity
aquired without an immune response
no antibodies produced
no memory cells
occurs when foetuses recieve antibodies from placenta
breast milk
what is artificial passive immunity
aquired without an immune response
no memory cells
can be a transfusion of antibodies collected from people with the tetanus vaccine
what type of virus is HIV
retrovirus - has the ability to make DNA/RNA
unable to survive out of human body
transmitted by the direct exchange of body fluids
what components make up an HIV molecule
2 RNA strands
proteins
protein capsid
viral lipid envelope
glycoproteins
proccess of viral replication
when the virus enters blood it infests helper t cells
helper t cells, inmstead of seeking out and destroying pathogens, it is now a host for the HIV
viral RNA enters thee cell
viral reverse transcriptase enzymes produce a DNA copy of the viral RNA
DNA is inserted into the chromosomes of the cell
each time the cell divides it copies the new DNA
infected cells can remain normal as viral DNA is inactive
how does HIV become dangerous
after a long time of hiding in t helper cells, the viral DNA becomes active
takes control of the t helper
more HIV are produced
helper t cell dies
releasing many HIV particals
process repeats
body can no longer fight against any infections (AIDS)
symptoms of AIDs
immediately after infection - flu like symptoms which pass
number of t cells gradually reduced
helper t cells play an important role in the immune system
can no longer produce antibodies
may be attacked by an oppurtunist disease
treatments of AIDS
drugs at slowing the rate of virus spreading
no cure
why cant antibiotics be used against virus
non living so have no metabolism for antibiotics to act on and disriupt
Uses of monoclonal antibodies
Pregnancy tests
Diagnosing HIV
Detecting the presence of bacteria
Blood typing
Distinguishing between herpes 1 and 2
Process of using monoclonal antibodies to locate the position of blood clots for patients
Infect mouse with human fibrin (the protein found in blood clots)
This activates the plasma cells to produce antibodies against fibrin
Cells are collected in the mouse spleen
Plasma cells are fused with tumour cells to form hybridomas that make anti fibrin antibodies
To detect where the antibodies are binding to fibrin, radiation I attached to antibodies making them labelled radioactively
Gamma ray camera detects these abnormal radiation
Therapeutical uses of monoclonal antibodies
Treatment for rabies - purified antibodies are injected
Treatment of diseases caused by the overproduction of B-cells - antibody binds to the cell surface receptor proteins on b cells, causing the death of cells
Why is the use of monoclonal antibodies bad be=ut how can we overcome this issue
Initially the antibodies were produced by mice which triggers an immune response when put into humans
We overcame this issue by genetically modifying the antibody polypeptide chains so that the amino acid sequences are now human
Use of animals vaccines
All vaccines are tested on animals - unethical
Animal based substances are used in the production of vaccines
Human testing vaccines
Small risk of unpredictable side effects
Often paid to do the tests - ethical issues as people feel pressured to do them
Might have had the vaccine and think it works but it actually doesn’t
Side effects vaccines
Very small probability but some people don’t take
They are still protected by herd immunity
Parents refuse children to be vaccinated but this is ethically questionable
Ethical issues around monoclonal antibody therapy
New mca are tested on animals before they can move onto human trials
Animals produce the cells which mca use
MMR study controversy
Study linked autism with MMR vaccine only used 12 children - due to chance
He was also working with parents who were trying to sue pharmaceutical companies so it is likely the results were fixed
After the study there were measles outvbreaks and the number of children diagnosed with autism still continued to rise
However diagnosis of autism increased due to better diagnosing
Thus no link between MMR and Autism
Definition of a monoclonal antibody
Each clone of plasma cells produces just one type of antibody - a mca
Example of indirect elisa test
HIV antigens are bound to the reaction vessel
Blood plasma is taken from the patient and added to reaction vessel
HIV specific antibodies will bind to the HIV antigens
Any other antibodies are washed out
A second antibody with an enzyme attached is added the the vessel and bind with primary
Washed out to remove unbound - avoids false positives
Substrate put into vessel - if there is any antibodies binding the substrate will be hydrolysed by the enzyme producing a colour
Direct elisa test
Same as indirect however the antibodies are bound to the bottom of the reaction vessel, an antigen will bind to this then another antibody with enzyme then substrate with washing out between each step.
