immune response Flashcards
what is the process called by which bacteria multiply?
binary fission
how do viruses multiply?
enter the host cell and use the host cells DNA replication and protein production to produce new viral particles
the specific immune response
detection of pathogens or antigens that involves white blood cells called B lymphocytes (B cells) and T lymphocytes (T cells)
Where do B lymphocytes originate and mature
bone marrow
where do T lymphocytes originate and mature
originate in bone marrow
mature in thymus
what do these lymphocytes have on there cell surface membranes
specialised protein receptor molecules
complementary to the shape of one specific antigen
what is clonal selection
selection: lymphocyte with complementary protein receptors to those of the antigens is selected when the antigen binds to those receptors
cloning: these selected lymphocytes are then stimulated to divide by mitosis
the specific immune response is divided into
cell mediated immunity
humoral immunity
these responses occur at the same time
what do T lyphocytes respond to
an organisms own cells that have been infected by a pathogen
cell mediated immunity
T cell response
cell mediated immunity
1
phagocytes that have engulfed some of the pathogen and any infected body cells place some of the pathogens antigens on their cell surface
this is called antigen representation
cell mediated immunity
2
the specific helper T cell with the specific receptor for the antigen come in contact with these anti gen presenting cells and the receptor T H binds with the antigen
this is the selection of the correct T lymphocyte
cell mediated immunity
3
this selection activates and stimulates the selected T cell to divide rapidly by mitosis- to clone
cell mediated immunity
4
these cloned T H cells:
- form T memory cells
- stimulate phagocytosis
- stimulate B cells to divide and produce antibodies
- activate cytotoxic T cells
cell mediated immunity
5
activated cytotoxic T cells kill infected cells by producing a protein called perforin that makes holes in the cell surface membrane
when holes are made in the cell surface membrane how does it affect the cell surface and what will happen to the cell
cell becomes permeable
allows water and solutes to enter and exit cell freely
cell will die
what type of pathogen is the cell mediated response most likely to be effective against and why
viruses as they replicate inside host cells
why might T cells respond to transplanted tissues from individuals of the same species
different individuals have different antigens on the surface of their cells
so tissues are recognised as non self
why might T cells be able to destroy body cells which have become cancerous
mutations in genes coding for (membrane) proteins will cause a different shape from a normal and be seen as non self
humoral immunity
B cells
humour
another word for bodily fluids
how do B cells respond to infection
by producing antibodies
humoral immunity
1
an antigen enters the blood
humoral immunity
2
there will be one B cell that has a specific antibody on its surface whose shape fits the antigen
the shapes are complementary
humoral immunity
3
the specific B cell takes in these antigens by endocytosis and presents them on the surface of the cell
humoral immunity
4
a specific helper T cell attaches and stimulates this B cell to divide by mitosis to form a clone of B cells by releasing cytokines (small proteins)
humoral immunity
5
the cloned B cells develop/ differentiate into:
plasma cells
B memory cells
plasma cells
these cells produce and release/ secrete antibodies specific to the antigen into the blood plasma
the production of these as well as B memory cells is the primary response
B memory cells
these enable an increased and more rapid response to a second exposure to infection
this is called secondary response
Antibody structure
- Made up of 4 polypeptide chains (2 light and 2 heavy)
- a constant region (same in all antibodies)
- a variable region (specific shape due to its amino acid sequence- ensures antibody attaches to the correct antigen)
- hinge region allows antibody to attach to more then one antigen
Where do antibodies bind to antigens?
Antigen binding site
What dowe call an antibody joined to an antigen?
Antibody-antigen complex
Agglutination of bacterial cells
One way antibodies can destroy pathogens
Primary response
- First time the immune system encounters a pathogen
- Cloning of the B cell takes time as there is only very few specific to antigen to begin with
- antibodies are secreted into the blood at a rate of around 2000 per second
- antibodies attach to and destroy pathogens and any antigens they produce
- plasma cells only survive a few days
- memory cells survive long after primary response
Secondary response
- Many memory cells remaining in the blood increase the chance of B cent of the correct type meeting with the pathogen
- response is much greater and more rapid than primary response
What type of cell is responsible for the primary response?
Plasma cells
Primary stages of vaccination
Phagocytosis
Presentation of antigen
clonal selection
Complementary T and B cells
Differentiation
What will the immune system produce as a result of vaccination
Antibodies
Memory cells
Antigenic material used in vaccines may be
Whole, living organisms
A harmless or attenuated version of the pathogenic organism
A dead pathogen
A preparation of antigens from a pathogen
Some harmless toxin
Active immunity
Produced by stimulation of production of antibodies and memory cells by the body’s immune system
Natural active immunity
Arises due to a response by the immune system to infection
Artificial active immunity
Arises due to a response by the immune system to vaccination
Passive immunity
Produced when antibodies are introduced from an outside source
e.g.
Maternal antibodies passed down to foetus
Anti venom given to shake bite victims destroys the toxin
Why should people who are at risk of developing serious complications from flu have a flu vaccination every year?
Virus mutates frequently
Can cause it to have different shaped antigens
So will no longer be effective
Herd immunity
Large enough proportion of the population have been vaccinated then it becomes difficult for a pathogen to spread
Ethics of using vaccines
Use of animals
Testing vaccines
Should be made compulsory?
Cost
Main problems with the study linking MMR vaccine with autism
Author was paid by legal aid board
Sample size was very small
More recent study has shown no link
Journal now says they would not publish now it knows all of the facts
How can the public know when to trust research?
Peerview
Source of funding
Personal beliefs
Media presentation
New theories may challenge current beliefs
monoclonal antibodies
specific antibodies
produced outside the body
used to treat diseases medically
uses of monoclonal antibodies
targeting medication
direct monoclonal antibody therapy
indirect monoclonal antibody therapy
medical diagnosis
pregnancy testing
direct monoclonal antibody therapy
monoclonal antibody is produced that is specific to the antigen
antibodies are given to patient and attach to the receptors on the cell surface membrane
this blocks chemical signals that stimulate uncontrolled cell growth
indirect monoclonal antibody therapy
monoclonal antibodies produced that are specific to antigen
radioactive or cytotoxic drug is attached to antibody and given to patient
targets cancer cells thus limiting damage to normal cells
medical diagnosis
e.g.
influenza
hepatitis
chlamydia
certain cancers
pregnancy testing
- urine of prego contains hormone human chorionic gonadotrophin
- pego testing strips have antibodies to hCG linked to an enzyme bound in the strip
- strip dipped in urine any hCG travels up strip and binds with the anti- hCG antibody
- this complex travels further up the strip binds with an immobilised second anti- hCG antibody
- enzyme is held in place to convert a colourless substrate into a coloured substance that appears as a band on the strip
ELISA meaning
enzyme linked immunosorbent assay
ELISA
- test sample antigens are attached to a well in test dish
- unattached antigens are washed off
- antibody to the antigen to be detected is added
4.excess antibody is washed off - a second antibody that only binds with the first and has an enzyme attached is added
- excess antibody is washed off
- colourless substrate to the enzyme is added- the enzyme acts on substrate to form a coloured product
- the amount of antigen present is relative to the intensity of colour
ethics of using monoclonal antibodies
the use of animals
have successfully treated cancer and diabetes
use in the treatment of multiple sclerosis has resulted in some deaths
using healthy vols may result in dangers
HIV
human immunodeficiency virus
how is HIV transmitted?
unprotected sex with someone infected
infected needles
mother to child
blood transfusion
where is the HIV virus found in the body
bodily fluids
does not live long outside the body
HIV cure?
no cure for HIV
treatments are available that enable people with the virus to live a long and healthy life
AIDS
acquired immune deficiency syndrome
final stage of HIV infection
How HIV causes the symptoms of AIDS
HIV directly attacks cells such as T helper cells
HIV infected cells die only after releasing replicated viruses which infect other T H cells
over time the number of T H cells decreases
what is the effect of low levels of T H cells in terms of the other cells in immune response
phacocytosis will not be stimulated
B cells are not stimulated to produce antibodies
cytotoxic T cells are not stimulated to attack infected cells
AIDS infected individual in terms of response long term
will experience infections and other life threatening illnesses
what kills people with AIDS
one of more diseases
testing for HIV
HIV test may detect the presence of HIV antigens,
antibodies or genetic material of HIV
after original infection it takes 2 weeks to 6 months for antibodies to HIV to appear in blood
one test is the ELISA test
structure of HIV
outside is lipid envelope with peg like attachment proteins
core is a capsid which contains the genetic material- two single strands of RNA
also in the capsid are enzymes required for HIV replication called reverse transcriptase, integrase and protease
the life cycle of HIV in a T H cell
- virus particle bumps into a T helper cell that carries on its surface a receptor protein called CD4
- the attachment glycoprotein on the surface of the HIV particle stick to the CD4 and this allows HIV to fuse with the cell membrane
- contents of HIV capsid released into cell
- HIV enzyme reverse transcriptase copies viral RNA into single stranded DNA and then into double stranded DNA
- this DNA is carried onto the cells nucleus through a nuclear pore and inserted into human DNA by the viral enzyme integrase
- viral genes are copied alongside human genes to make copies of viral messenger RNA for the viral genome
- this is transported outside the nucleus and used to produce viral proteins using human ribosomes
- copies of the HIV genetic material and newly made HIV proteins and enzymes assemble at the cells surface and form new viral particles
- these are released from the cells in a process known as budding
- new HIV particles are now ready to infect other cells
why are antibiotics ineffective against viral diseases like AIDS
viruses are not cells and don’t have cell walls
antibiotics weaken bacterial cells wall so it no longer withstands expansion as water moves in by osmosis
bacterial cell bursts and bacteria dies
