celll recognition and the immune system

what is an infection
interaction between pathogen and bodys various defense mechanisms
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what is immunity
where the body defense system is better prepared for a second infection from the same pathogen
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what are the two repsonces
cell mediated involving t lymphocytes and humoral repsonse involving b lymphocytes
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what lymphocytes do humoral responce inolce
b
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what lymphocytes do cell mediated response involve
t
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how do lymphocytes distinguish bodys own cells and foreign cells
each cell has sepcific molecules on its surface that identify it, the proteins have highlyspecific tertiary structure
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whatsa problem with poeple who have had transplasts
immune system recognises them as non-self and attempts to destroy it
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how to minimise effect of transplant rejection
donor matched closely, immunosupprecient drugs
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what is important to remember about specificlymphocytes
not produced in response to an infection, alreaady exist
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when an infection occurs, what do the lymphocytes already have
complementary proteins to those of pathogen
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non specific defense mechanism and example
response is immediate and same for all pathogens, skin and phagocytosis
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specific defense mechanism and example
repsonse is slower and specific to each pathogen, 2 types of responses
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what are the lymphocytes doing in the fetus
constantly colliding with other cells, and thereofre own material
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why is infeection in fetus rare
protected from the outside worldby mother and placenta
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what happens to remain lymphocytes
might fit forgin material
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what happens to lymphocytes produced in the bone marrow
onnly encounter self-antigens
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what happens to lymphocytes that show an immune repsonse to self antigens
undergo programmed cell death (apoptosis) before they differentiate into mature ones
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what are the two types of white blood cell
phagocytes and lymphocytes
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what do phagocytes do
ingest anddestroy pathogen by phagocytosis
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what do lymphocytes do
involved in immune responses
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whatis phagocytosis
large particles engulfed by cells in the vesicles fromed from the cell-surface membrane. phagocytes carry this out
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where do phyagocytes travel
bloodbut can move into tissues
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process of phagocytosis
phagocyte attracted to pathogen by chemical products, moving along a concentration gradient. phagocytes has receptors that attatch to chemicals of pathogen. lysosomes within phagocyte form phagosome englufing bacterium and release lysozymes
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process of phagocytosis after lysozymes are released
they hydrolyse the bacterium which those producs are absorbed by phagocyte
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what is immunity
ability of organsisms to resist infection by protecting against disease-causing microorganisms or toxins which invade the body
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what is an antigen
any part of an organism or substance that is recognised as non-self and stimulates an immune response (proteins)
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what does immune response depend on
type of white bood cell called lymphocyte
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where are lymphocytes produced
produced by stem cells in bone marrow
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what are b lymphocytes
mature in Bone marrow, humoral immunity which involvesother antibodies present in the body in fluids or 'humour' such as blood plasma
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what are t lymphocytes
mature in Thymus gland. cell mediated immunity, immunity in body cells
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why is there a response the cells from other individuals of same species
genetically different, having different antigens
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how can t lymphocytes distinguish invader cells from normal cells
different antigens on cell surface membrane
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what are antigen presenting cells
cells that display foregin antigens on their surface
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another name for cell mediated immunity
cellular response
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why are receptors in t cells important
receptors on each t cell repsond to a single antigen
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stage of t lymphocyte response
pathogens invade body cells and phagocyte places antigens from pathogen on surface, recepter on helper r t cells fit these antigens. attatchment activates t cell to divide rapidly by mitosis anf from clone
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what do clone of t cells develop into
memory cells that enable rapid response in future, stimulate pathocyte to engult pathogens, activate cytotoxic cells
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what are cytotoxic cells
kill abnormal body cells infected by pathogens by producing perforin that makes holes in the cell meaning cell membrane becomes freely permeable which means cell dies.
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how does antigen entre b cell
enocytosis
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what happen in humeral immunity
th cells bind to these processedantigens and stimulate b cells to devide by mitosis to from a clone of identical b cells
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whats monocloal antibodies
each clone produces one specific antibody
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what are plasma cells
secrete antibodies into blood, lead to destruction of antigen
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what are memory cells
circulate in blood and tissue fluid, when encounter same antigen they divide rapidly and develop into plasma cells and more memory cells
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what are antibodies
preteins with specfic binding sites synthesis by b cells. reacts with n anitgen by binding.
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how many binding sites do antigens have
2 which are complementary
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structure of antibodies
4 polypeptide chains, 2 long which are heavy chains and 2 short called light chains
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whats an antigen antibody complex
specific binding site that fits very precisely onto a specific antigen
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what does each binding site consist of
sequence of amino acids that from 3d shape that binds directly to a specifc antigen
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what is rest of antibody known as
constant regeion which binds to receptors
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how does te antibody lead to destruction of the antigen
dont directly destroy but prepare for them to be. cause agglutination where clumps of bacterial cells are formed which makes them easier to locate then they serve as markers that stimulate phagocytosis
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what are monnoclonal antibodies
antibody produced by a single clone of cells
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why are monoclonal antibodies useful
used to target specific substances and specific cells
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whats direct clonal antibody therapy
theyare produced that are specific to antigens on cancer cells, antibodies given to aptient adn attatch to receptors on caner cells, blok chemical signals that stimulate uncontrolled growth
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what treats breast cancer
herceptin
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advantage of direct monoclonal antibodies
not toxic and specific, fewer side effects
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indirect monoclonal antibody therapy
attatching radioactive or cytotoxic drug to monoclonal antibody, which attaches to cancer cells to kill them
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how are monoclonal antibodies used in medial diagnosis
interacts with antigen, possible to obtain a measure of the level of PSA in a sample of blood (eg prostate specific antigen)
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how monoclone antibodies are used in pregnancy testing
placenta produces a hormone call hcg found in urine. monoclonal antibodies are present on test ***** are linked to cloured particles. if hormones is present it binds so moves along the line untill trapped by a different type of antibody creating line
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uses of monoclonal antibodies
killing cancer cells (2 ways), medical diagnosis, pregnancy testing
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ethical issues of monoclonal antibodies
producing them uses mice for testing, deliberate tumour growth. death involved associated in use of treament. testing drugs present dangers
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2 forms of immunity
passive and active
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passive immunity
produced by introduction of antibodies into individual from outside source. no direct contact with the pathogen or its antigen is necessary. immunity is immediate
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active immunity
produced by stimulating the prodcution of antibodies by individuals own immune system. direct contact is necessary and there is 2 types (natural and artificial)
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natural active immunity
restults from an individual becoming infected with a disease under noraml circumstances
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artificial immunity
introducing an immune response in an individual, without them suffering sympton of disease
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what is a vaccination
introduction of appropriate disease antigens into the body, by injection or mouth. memory cells produced which remain in the blood
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what is a vaccine
material introduced in a vaccination
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aim of vaccination
stimulate an immune response against a particular disease
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what succes of vaccination programme depends on
economically available in sufficient quantities, few side effects, sorage and transporting must be available.
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what is herd immunity
suficiently large proportions of population has been vaccinated making it difficult for pathogen to spread
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why is herd immunity important
never possible to vaccinate everyone in a large proportion. babies arnt because their immune system isnt developed and dangerouhs to poeple who are ill
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how to achieve herd immunity
vacination carried out one at a time
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why can it still be difficult to get rid of a disease after vaccination
fail to inttroduce immunity, individuals may develop disease immediatly before levels are high, pathogen may mutate, impossible to develop vaccine for every pathogen, some pathogens hide, individuals may have objections
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ethics of using vaccinations
involves use of animals, side effects, unknown health risks, is it right for everyone to be vaccinated, expensive
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what does aids stand for
acquired immune deficiency syndrome
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hiv stands for ?
human immunodeficieny virus
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structure of hiv
outside is a lipid envelope with attathcment proteins. inside is capsid that encloses two strands of RNA and enzymes. one enzyme is reverse transcript
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what is a reverse transcript
catalyses production of dna from rna- reverse reation of transcriptase gives hiv ability to make dna from rna
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what grouop does hiv belong too
retroviruses
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why cant hiv replicate
its a virus so it uses genetic material to instruct host cells biochemical mechanismsto produce components required to make new HIV
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how does it replicate
hiv entres bloodstream and circulates around the bodym protein on hiv binds to protein called CD4, protein capsid fuses with the cell-surface membrane so rna and enzymes of hiv enter the helper t cell. RT converts rna to dna
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what happens to dna once made by reverse transcript
moved into helper t cell nucleus where it is inserted onto the cels dna. hiv dna in nucleus creates messenger rna using cells enzymes. it contains instructions making new viral proteins and rna to go into new hiv
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how does messenger rna leave
pass out nuclear pores and uses cell proteinsynthesis mechanisms to make hiv particles. particles break away from helper t cell with piece of cell surface membrane surrounding with forms their lipid envelope
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how hiv causes aids
by killing or interfering with the normal functioning of helper t cells
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result of little helper t cells
immune system cannot stimulate b cells to produce antibodies or cytotoxic cells that kill cells affected by pathogens
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what does ELISA teset stand for
enzyme linked immunosorbant assay.
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what does elisa test do
uses antibodies to not only detect presence of a protein in a smaple but also quantity and also detect hiv
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how does elisa test work
apply sample to surface so antigens will attatch, wash surface to remove unattatched antigens, add antibody specific to antigen, wash again, add second anibody with enzyme attatched, add colour substrate
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what does colour depend on
amount of antigen present, relative to intensity of colour that develops
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why are antobiotics ineffective against viral diseases
they inhibit certain enzymes required for the synthesis and assembly of poly peptide cross linkages in bacterial cell walls, weakens the walls making them unable to hold pressure
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what mechanisms do antibiotics lack
metabolic which viruses rely on host cells to carry out their metabolic activities
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what coat do viruses have
proetin not murein so dont have sites where antibiotics can work
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