cell recognition and the immune system(cells) Flashcards
what are the two types of white blood cell
phagocytes and lymphocytes (phagocytes are the type of white blood cell to carry out phagocytosis and lymphocytes are the type responsible for the immune response (they become activated in the prescence of antigens )
what happens with lymphocytes during development
millions of different lymphocytes , rare for pathogens to be found and lymphocytes collide with own cells , these then go through apoptosis (programmed cell death) and left behind are those that fit ‘non self’ cells
what are the types of defence mechanisms
non specific - physical and chemical barries and phagocytosis
specific - cell- mediated and humoral
what are some barriers
skin , mucus , hairs , cillia , stomach acid ,
what is the defenition of a pathogen
any microorganism that causes disease
what is the defenition for immunity
the means by which the body protects itself from infection
what is the defenition for phagocytes
the type of white blood cells that carry out phagocytosis
what is the defenition for lymphocytes
types of white blood cell responsible for the immune response . they become activated in the prescence of antigens (B and T)
what is the defenition of a phagosome
they engulf the pathogen to form a vesicle known as a phagosome
what is the defenition for a lysozyme
enzymes present within the lysosome . these destroy ingested bacteria by hydrolysis or their cell walls
what is the defenition for phagocytosis
mechanism by which cells engulf particles to form a vesicle
what is the defenition of a vesicle
a small structure within a cell , consisting of fluid enclosed by a lipid bilayer
what are antigens
attachment proteins
what are the steps for phagocytosis
- phagocyte detects foreign antigens by detecting chemicals released by the pathogen and the chemical concentration gradient (chemotaxis)
- the phagocyte starts to engulf the pathogen and attaches by receptors
- this creates a phagosome (vesicle)
- the lysosomes fuse to the phagosome and they release lysozymes (exocytosis )and hydrolyse the pathogen cell wall
- debris is released and it becomes an antigen presenting cell.
what is the role of T lymphocytes
respond to body cells with foregin antigens
What are the two types of lymphocytes
T lymphocytes ( cell mediated ) and B lymphocytes(B lymphocytes)
what are the steps after phagocytosis
a receptor on a T helper cell binds to foregin antigen on APC. this forms an activated T helper cell which divides by mitosis to create many clones which can differentiate into different cells
what are the different cells a T helper cell can differentiate into
can form memory cells , stimulate more phagocytosis , stimulate B cells to divide , activate cytotoxic t cells
how can cytotoxic t cells destroy infected cells
cytotoxic t cells can bind to infected cells and release perforin which makes holes in infected cells membrane . this causes the infected cell to be destroyed as the cell membrane becomes freely permeable to all substances and the cell dies.
where do T cells mature
in the thymus gland
what is the definition for antigen presenting cells
cells that display forgein antigens on their surface
cell - mediated immunity is the response of T lymphocytes , what does this mean
lymphocytes will only respond to antigens that are presented on a body cell rather than antigens within bodily fluids .
what are examples of APC cells
infected body cells , a phagocyte , cells of a transplanted organ and cancer cells
what are antibodies
quaternary proteins made of 4 polypeptide chains so it can perform its function
what are the parts of an antibody
light polypeptide chain and heavy polypeptide chain . a constant region and a variable region which changes for different antibodies
how are the chains attached in an antibody
by disulfide bridges
how is the binding site made on an antibody
the variable regions form the antigen binding sites. they have 2 binding sites so can attach 2 antigens. the specififc binding sit fits very precicely onto a specific antigen
what is it called when an antigen attaches to an antibody
antigen - antibody complex
what are the 4 main functions of antibodies
- agglutination - antibodies can attach to pathogens antigens and stick them together to form a clump which makes it easier for the phagocytes to destroy them . attracting phagocytes (antibodies dont do any destruction)
opsonins - tagging foreign bodies for phagocytosis
antitoxins - binding to toxins and neutralising them
why is the massive variety of antibodies possible
because they are made of proteins - molecules that occur in an almost infinite number of forms
What is the primary immune response l
Plasma cells - produce antibodies
What is the secondary immune response
Memory cells
What are the stages of the specific response
1) the surface antigens of an invading pathogen are taken up by a b cell
2) the b cell processes the antigens and presents them on its surface
3)helper T cells attach to the processed antigens on the b cell thereby activating the b cell
4) the b cell divides by mitosis to clone into plasma cells or memory cells
5)the cloned plasma cells produce and secrete the specific antibody that exactly fits the antigen on the pathogens surface
6) the antibody attaches to antigens on the pathogen
7) some b cells develop into memory cells which can respond to future infections by dividing rapidly and developing into plasma cells that produce antibodies . This is the secondary immune response
Antibodies are examples of globular proteins . Explain how a change in the primary structure of a globular protein may result in a different 3 dimensional structure, and the consequence of this on the immune response ( 5 marks)
Primary structure is the sequence of amino acids , this determines positioning of bonds . This determines the shape of the variable region . Variable region is specific to one type of antigen . Change can mean the antigen can no longer bind /no antigen -antibody complex formed so pathogen no longer destroyed
What does mono clonal antibody mean
One clone antibody
What is a monoclonal antibody
Antibodies produced outside the body , produced from a type of cloned cell , diagnostic and therapeutic uses
What does the ELISA test stand for
Enzyme linked immunosorbant assay
What does the ELISA test do
It can detect the presence of a protein in a sample and also the quantity . It is very sensitive and so can detect very small amounts of a molecule
What are the steps to the ELISA test
1) apply the sample to a surface . Eg a slide to which all the antigens in the sample will attach
2) wash the surface several times to remove any unattached antigens
3) add the antibody that is specific to the antigen we are trying to detect and leave the two to bind together
4) wash plate to remove excess antibody
5) add monoclonal antibodies with enzymes attached then wash
6)add the substrate and there will be a colour change if enzymes and substrate attach
7) the amount of antigen present is relative to the intensity of the colour change that develops
What are the uses (specific) of the elisa test
Detect HIV , tuberculosis and hepatitis
When is ELISA especially useful
When the quantity of an antigen needs to be measured
How is HIV transmitted
Through blood , sharing needles , sexual contact (unprotected sex) , passed from mother to baby
What are the symptoms of ADIS
Sore throat , muscle aches , rash , fever , chills , swollen lymph nodes , fatigue , mouth ulcers , night sweats
What is the structure of the HIV virus
2 strands of RNA , reverse transcriptase enzyme , glycoproteins gp20 ( attachment proteins ) , capsid , lipid envelope , matrix
What does HIV stand for
Human immunodeficiency virus
What is reverse transcriptase
An enzyme located in the HIV virus which catalyses the production of DNA from RNA
How does HIV cause aids
Hiv specifically attacks t helper cells , HIV causes AIDS by killing or interfering with the normal functioning of T helper cells . Without a sufficient number of T helper cells the immune system cannot stimulate B cells to produce antibodies , the cytotoxic T cells that kills cells infected by pathogens , memory cells may also become infected and destroyed . As a result the body is unable to produce an adequate immune response and becomes susceptible to other infections and cancers .
Why are antibiotics ineffective against viral diseases like AIDS
Viruses lack their own metabolic pathways and cell structures as they rely on a hosts cell . Therefore antibiotics are ineffective because there are no metabolic mechanisms or cell structures for them to disrupt . Additionally when viruses are in an organisms own cells , antibiotics cannot reach them
Explain why HIV is called a retrovirus
Because it possessed RNA and the enzyme reverse transcriptase which can make DNA from RNA - a reaction that is the reverse of that carried out by transcriptase
Distinguish between HIV and AIDS
Hiv is a virus , AIDS describes the condition caused by the infection with HIV
How does HIV replicate
Hiv virus attachment proteins attaches to receptors on a T lymphocyte as they are complementary
The hiv virus then fuses with the T lymphocyte and releases the capsid into the T lymphocyte which becomes a hosts cell
Reverse transcriptase copies the strand to form DNA from RNA .
The lipid envelope forms from the cell membrane of the T helper cell
This allows the virus to replicate , eventually the HIV virus destroys the T helper cell
What are the two forms of immunity
Passive immunity and active immunity
Describe passive immunity
Produced by the introduction of antibodies into individuals from an outside source.
( immune system is not activated ) . No direct contact with the pathogen is required . Immunity is acquired immediately however as the antibodies are not being produced by the individual themselves , the antibodies are not replaced when they are broken down . So no memory cells are formed and there is no lasting immunity . Eg mother to baby antibodies
Describe active immunity
Is produced by stimulating the production of antibodies by the individuals own immune system
Describe natural active immunity
Results from an individual being infected with a disease under normal circumstances the body produces its own antibodies and may continue to do so for many years
Describe artificial active immunity
Forms the basis of vaccination it involves inducing an immune response in an individual without them suffering the symptoms of the disease
What is here immunity
Arises when a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread within that population
What are the ethical issues of vaccines
Often involve the use of animals , side effects which could cause long term harm
What is a monoclonal antibody
Antibodies with the same tertiary structure
