3.2.4 immunology Flashcards
what is the first stage of phagocytosis?
the phagocyte is attracted to the pathogen by the toxins and chemoattractants it releases and moves towards it
what is the second stage of phagocytosis?
the phagocyte engulfs the pathogen and forms a vacuole around it
what is the third stage of phagocytosis?
the phagocyte takes the pathogen into its cell and forms a phagosome
what is the fourth stage of phagocytosis?
the lysosome fuses with the phagosome and secretes lysozymes to hydrolyse and destroy it
what is phagocytosis?
the non specific response
what is the final stage of phagocytosis?
the pathogens antigens are presented to the surface of the phagocyte
what are the functions of T cells? (4 points)
produces memory T cells, stimulated phagocytosis, kills infected cells (making holes in their membrane), stimulates B cells to divide
how can B cells act as antigen presenting cells?
B cell with an antibody that is complementary to the antigen, takes up the surface antigens of the invading pathogens, the processed antigen is presented on the surface of the B cell
how do activated T helper cells work?
they attach to the processed antigens on the B cells thereby activating them, the B cells will then divide by mitosis to produce clones and differentiate into memory cells or plasma cells
what are the two types of B cells?
memory cells and plasma cells
how do B cells divide?
by mitosis to produce clones
what are memory b cells?
circulate in the blood and tissue fluid in readiness to respond to a future infection by the same pathogen
what are plasma b cells?
produce antibodies that exactly fit the antigens on the pathogens surface, the antibodies attach to the antigens on the pathogen to destroy them
what is the secondary response?
if the same infection occurs again the memory cells divide and develop into plasma cells that produce antibodies, this secondary infection produces antibodies (in plasma cells) in higher concentrations and more quickly
what is the role of antibodies (3 points)?
coat the pathogen with antibodies to make it easier for the phagocyte to engulf, coat the pathogen with with antibodies to prevent it from entering the body cells, antibodies bind to and neutralise (inactivate) toxins produces by the pathogen
how do B cells and T cells work together?
both b cells and t cells are required to remove a pathogen from the body, the responses interact with each other, t cells activate b cells and antibodies coat pathogens making it easier for phagocytes to engulf them
what is the structure of an antibody?
antigen binding sites, light chain, heavy chain, variable region, constant region, receptor binding site
what is the variable regions?
since the binding sites differ they are called the variable region, the sequence of amino acids give each variable region its specific 3D shape
what is the constant region?
binds to receptors
how is an antigen-antibody complex formed?
each binding site is complementary to a specific antigen
why will the antibody only detect a specific antigen?
the antigen binding site is complementary to the antigen as the variable region has a specific amino acid sequence to form an antigen-antibody complex
what is agglutination?
antibodies clump bacterial cells together so it is easier for phagocytes to locate and engulf as they are less spread out
how to antibodies act as markers?
they act as markers that stimulate phagocytosis, phagocytes can engulf the pathogen easier as they are attached
what are polyclonal antibodies?
pathogens can have many antigens on their surface that can activate many plasma b cells, each of these b cells will clone to produce different antibodies, these are collectively known as polyclonal antibodies
what are monoclonal antibodies?
a single type of antibody that is clones on mass outside of the body, from one type of b cell
what is meant by immunity?
the ability of an organism to resist infection
what are the two forms of immunity?
active and passive immunity
what is passive immunity?
antibodies introduced from an outside source, antibodies are not produces by the individual so they are broken down, no memory cells so short lived
what are examples of passive immunity?
anti-venom, immunity acquired by a foetus from the mother
what is active immunity?
production of antibodies is stimulated by the individual, direct contact with the pathogen/antigen, immunity takes time to develop, long lasting
what are the two types of active immunity?
natural and artificial active immunity
what is natural active immunity?
individual infected with a disease, normal immune response
what is artificial active immunity?
vaccination, induced immune response, few symptoms
what do vaccinations involve?
purring a vaccine into the body that will generate an immune response
how are vaccines administered?
orally or subcutaneously (injection)
what do vaccines contain?
antigens to lead to the production of memory cells
how are vaccination programmes successful?
must be cheap enough to immunise all vulnerable populations, few side affects so people aren’t discouraged, ability to produce/store/transport vaccine (hi-tech equipment), must be administered correctly at the appropriate time; trained staff are required, vaccinate the majority of population; best at one time so that for a period no individual carries the disease (transmission interrupted/ herd immunity)
what is herd immunity?
large enough proportion vaccinated makes it difficult for the disease to spread, vaccination population provide a measure of protection for individuals who have not developed immunity, the greater proportion vaccinated means smaller probability that unvaccinated people com into contact with the pathogen
when is herd immunity best achieved?
when vaccinations are carried out at one time, for a short period there are few infected individuals, interrupting transmission
why do vaccinations not eliminate a disease?
don’t induce immunity in some individuals, disease can develop before immunity achieved, pathogens mutate frequently, pathogen varieties, pathogens hide from the immune system, individuals object to vaccination
why do vaccinations not induce immunity in some individuals?
immune system defects
why does pathogen mutation mean that vaccination doesn’t eliminate a disease?
mutation changes antigens, vaccine ineffective as new antigens are not recognised, antibodies are not produced, antigenic variation happens regularly in the influenza virus, immunity is short lives and repeat infections are common
why do pathogen varieties mean vaccination does not eliminate disease?
difficult to create vaccines for all, 100 varieties of common cold
how do pathogens hide from the immune system?
hide in cells or live in the gut where they are difficult to kill e.g. cholera
why do some individuals object to vaccinations?
Religious, ethical, medical, safety concerns
What are the ethical issues of vaccinations?
Animals use in development, side-effects can cause long-term harm, who should vaccines be tested on, is it fair to test on population where target disease is common based on the idea they will gain the most benefit if it’s successful, is it right to make vaccinations compulsory, should expensive vaccination programs continue when the disease is almost eradicated
how are tumour cells produced for monoclonal antibodies?
irradiate mouse to induce formation of tumours, tumours form inside the mouse and the cells are removed
how are the B cells produced for monoclonal antibodies?
inject a different mouse with non-self antigens, B cells which produce antibodies against the antigens are removed from the spleen
how are hybridomas formed?
mix tumour cells with B cells and add detergent, detergent caused cells to fuse
what are the features of the fused cells (monoclonal antibodies)?
have features of tumour and B cells- ‘immortal’ and produce antibodies
how are monoclonal antibodies made ready for use?
fused cells are separated and cultured to form clones, each clone is tested to identify which one is producing the required antibody, culture the selected cells on a large scale and humanise them
what is meant by humanisation?
the cells have to be modified to make them mor like human cells before they can be used as they come from a mouse
what are the uses of monoclonal antibodies?
separating chemicals form mixtures, immunoassay (detecting concentrations of macromolecules in solutions), cancer treatment, transplant surgery
what does HIV stand for?
human immunodeficiency virus
what does HIV cause?
causes AIDS (acquired immunodeficiency syndrome)
how does HIV affect the immune system?
gradually destroys the sufferers immune response
when did the HIV epidemic start?
in the 1980s
where did HIV come from?
western central africa, possibly in the 1930s, this virus jumped the species barrier, transferred from pronates to humans, possibly due to eating or slaughtering chimpanzees
how is someone infected by HIV?
enters the body via infected body fluids; during sexual intercourse, drug taking using infected needles, blood infection, blood transfusions and blood products, mother to child across the placenta during pregnancy and via breast milk
what are the symptoms of HIV?
fever (raised temperature), sore throat, body rash, tiredness, joint pain, muscle pain, swollen glands (nodes)
what are the symptoms of AIDS?
weight loss, chronic diarrhoea, night sweats, skin problems, recurrent infections, serious life threatening illnesses
what is the structure of the HIV virus? (7 points)
trans membrane glycoproteins, docking/attachment glycoproteins, lipid envelope, reverse transcriptase, matrix, caspid, genetic material (RNA)
what is the significance of reverse transcriptase enzyme?
enzyme that catalysed the production of DNA from RNA this ability means that HIV belongs to group called retroviruses
How does HIV infect host cells?
as HIV is a virus, it is unable to replicate on its own, it used its genetic material to instruct the host cells biochemical mechanisms to produce the parts needed to make HIV
what is the first stage of HIV infection?
p120 molecules (attachment glycoproteins) on the HIV bind to CD4 receptor proteins on the T helper lymphocytes and macrophages
what is the second stage of HIV infection?
the protein caspid fuses with the cell membrane
what is the third stage of HIV infection?
HIV RNA and enzymes enter the T cell
what is the fourth stage of HIV infection?
HIV reverse transcriptase converts the virus’s RNA to DNA
what is the fifth stage of HIV infection?
the new DNA is moved into the helper T cell’s nucleus where it is inserted into the cells DNA
what is the sixth stage of HIV infection?
the HIV DNA in the nucleus created mRNA containing instructions for making new viral proteins and the RNA for new HIV
what is the seventh stage of HIV infection?
the mRNA leaves the nucleus of the host cell through nuclear pores and uses the cells protein synthesis mechanisms to move HIV particles
what is the eighth stage of HIV infection?
the HIV particles bud away from the helper T cell with a piece of its cell surface membrane surrounding them which forms their lipid envelope
how does HIV lead to aids?
HIV specifically targets helper T cells, leads to AIDS by destroying/interfering with T cells normal functioning, since there are no longer enough helper T cells B cells are not stimulated to produce antibodies, cytotoxic T cells not stimulated, memory cells are also sometimes infected and destroyed
what does AIDS result in?
inadequate immune response, vulnerable to infections and cancer e.g. lungs, intestine, brain and eyes, diarrhoea and weight loss are common, secondary illness not HIV that causes death
where do T cells mature?
in the thymus gland
what is the cell mediated response?
immunity involving body cells, T lymphocytes responds to foreign material inside body cells/responds to own cells altered by viruses/cancer or transplanted tissue
which cells are targeted by T lymphocytes?
Antigen presenting cells; pathogens that have been engulfed and hydrolysed, phagocytes present some antigens on their surface. Body cells invaded by a virus present viral antigens. Cancer cells are different from normal cells and present antigens. Transplanted cells have different antigens
describe the process of the cell mediated response:
pathogens invade body cells or are taken in by pathogens, the phagocyte places antigens from the pathogen on its own surface membrane, receptors on certain helper T cells fit exactly onto these antigens, this activates other T cells to rapidly divide by mitosis and produce a clone
what happens to the cloned T clls in the cell mediated response
develop into memory cells for a faster future response, stimulate phagocytosis, stimulates B cells to divide into plasma cells and secrete antibodies, activate cytotoxic T cells
how do cytotoxic T cells work?
cytotoxic T cells kill abnormal body cells, produce a protein called perforin that makes holes in the cell surface membrane, makes the cell freely permeable, killing it by osmotic lysis, affective against viruses as they replicate inside cells
what is the ELISA test?
enzyme linked immunosorbant assay, uses antibodies to detect the presence and amount of protein in a sample, highly sensitive
what is the method for the ELISA test?
apply sample to surface, the antigens in the sample will attach to this surface, wash the surface to remove any antigens that arent attached, add the antibody that is specific to the antigen we are trying to detect, leave to allow binding, rinse to remove excess antibody, add a second antibody that will bind to the first antibody, the second antibody has an enzyme attached to it, add the substrrate to enzyme (colourless), the enzyme acts on the substrate, the substrate is converted into coloured products
describe the differences between immunity obtained from breastfeeding vs vaccines
immunity from breastfeeding is immediate but immunity from vaccines takes time to develop, a vaccine involves exposing a baby to an antigen whereas breastfeeding provides immunity without needing to expose the baby to an antigen, immunity from breastfeeding does not produce memory cells but vaccines do, immunity from breastfeeding short time but longer immunity from a vaccine
Where do B cells grow?
Bone marrow
Where do B cells mature?
The bone marrow
Where do T cells grow?
Bone marrow
Where do T cells mature?
Thymus gland
