cells and the immune system (p1) Flashcards
Each type of cell has ________ molecules on its ________ that identify
it.
Each type of cell has specific molecules on its surface that identify
it.
Antigens
-molecules that can generate an immune response when detected by the body
-found on the surafce of cells
-_ antigens that aren’t usually found in the body are forgein anitgens/ allow idetification of celg molecules and non-self molecules
-it is the specific 3d structure that distinguishes one cell from another.
antigens allow the immune system to identify
pathogens- all have antigens on their surface. which can be identified as foreign and destroyed
toxins- Are poisons. molecules not cells. is the antigen produces by bacteria. Immune system can respond to toxins and the pathogen that released them.
abnormal body cells- cancerous or pathogen-infected cells have abnormal antigens on surface triggers an immune response.
Cells from other organism of the same species/non-self material- cells reicved from anothrt person e.g transplant or blood transfusion. will have some antigens that are differnt from the recipient. foreign antigen trigger immune response.This can lead to rejection if immunosuppressant drugs aren’t taken.
Immune response
antigen—->immune response——> Immediate= non-specific (e.g phagocytosis,inflammation, antimicrobial proteins).———->delayed=specific (B cells, T cells)
Non-specific immune responses
-Fever
-inflammation
-interferon
-phagocytosis
-histamines
Histamines
-released by most cells/damaged white blood cells.
-cause blood vessles to dialate cause local heat and redness
-higher temp prevents pathogen from reproducing
-blood vessles more leaky,plasma forced out causing pain and swelling.
E.g hayfever- antigrn such as pollen = allergic response, histmine is relase. antihistamine reduce allergic response histmaine and is simular shape to antihistamine so antihistmine bind to histamine recpectore and prevent the histamine binding
Inflammation
-ofteninfection localised at one sight
-when tissue damaged white blood cells relase histamine, aterioles become leaky
-more wide spread= rash
inteferon
-produced by Cells infected by viruses anti-viral proteins called interferons
-Interferons prevent viruses from spreading to uninfected cells, bind to repetors of unaffected cells
-They inhibit the production of viral proteins, preventing the virus from replicating
-They activate white blood cells involved with the specific immune response to destroy infected cells-they increase the non-specific immune response e.g. by promoting inflammatio
Fever
-raise in body temperature
-helps kill pathogens prevents them reproducing
-specific response=better at a higher temp
lysozymes
-enzymes in tears saliva , nasal secretions
-kills bacteria by breaking down cell walls
a phagocyte (e.g a macrophage) is a type of ——– blood cell that carries out __________.found in blood and tissues and are first to respond to immune system trigger inside the body.
a phagocyte (e.g a macrophage) is a type of white blood cell that carries out phagocytosis.found in blood and tissues and are first to respond to immune system trigger inside the body.
steps phagocytosis
1)phagocyte recognises foreign antigens on pathogen
2)cytoplasm of the phagocyte moves around the pathogen engulfing it
3)The pathogen is now contained in the phagocytic vacuole in the cytoplasm of the
4)a lysosome fuses with the phagocytic vacuole and the lysosymes break down the pathogens.
5)the phagocyte presents the pathogens antigens-it sticks them to it’s surface to activate other immune systems cells. The phagocyte is acting as a antigen-presenting cell.
Types of white blood cells
neutrophils (70%)
lymphocytes (24%)
Monocytes (4%)
other white cells (2%)
neutrophils
(phagocytes)
-leave blood capillaries by squeezing between cells
-ingest and and destroy bacteria
-80 million produce a minute and last a few days.
lymphocyte
two types-B cells and T cells
-involved in immune response, including antibody production and immunity
-some last a few days others a few years
monocytes
-circulate in blood for a day or 2 before moving into tissue by squeezing out
-here they become macrophages and engulf bacteria, cell debris etc
-numerous in liver,kideny,spleen and lymphnodes.
lymphnodes
-where macrophages attack bacteria which have got into blood.
-if these don’t stop it then leads to septic shock/ blood poisoning.
the specific response involves
B lymphocytes and T lymphocytes
T lymphocytes
-made in the bone marrow
-mature in the thymus
-carry out the cell mediated immune response (cellular)
-this mean that can recognise and destroy abnormal cells
The response of T lymphcytes to a foreign ________ (the cellular response)
The response of T lymphocytes to a foreign antigen (the cellular response)
The response of B lymphocytes to a foreign antigen, clonal selection and the release of monoclonal _______ (the humoral response).
The response of B lymphocytes to a foreign antigen, clonal selection and the release of monoclonal antibodies (the humoral response).
B lymphocytes
-made in bone marrow
-mature in the bone marrow
-carry out humoral immune response
-this mean are responible for antibody production
cells that display foreign antigen on their surface
antigen presenting cells.
cell mediated immunity
T cells only respond to antigens presnted on a body cell
this is called cell mediated immunity/cellular repsonse
recpetors on each T cell respond to single antigen
summary of Helper T cells in cellular response
1.pathogen invades body cell/ is taken in by phagocytes
2.phagocyte places antigens from pathogen on its surface ( it is an antigen presenting cell)
3.Helper T cells receptors fits the particular antigen
4)attachment activates the t cell to divide by mitosis to form a clone of genetically identically cells
5) the cloned cells:
-become memory cells that circulate in bloof and tossue fluid in readiness to respond to future infection same pathogen
-stimulate b cells to divide
-stimulate phagocytosis by phagocytes
-activate cytotoxic t cells kill infection cells making holes in membrane
Helper T cells (need to know)
.help humoral response by involvement in maturation of B cellls and triggering the production of antibodies by b-cells.
.also trigger phagocytosis
cytotoxic t cells
-kill abnormal cells that are infected by pathogens, by producing a protein called perfarin that makes holes in the cell-surface membrane, meaning it becomes fully permeablr to alll substances and the cell dies as a result.
Memory T-cells (not require)
work in same way as memory b celld,ensure rapid response on subsequent exposure to the same non-self antigens.
Suppressor T-cells (not rquired)
reguales the immune reponse by suppressing the activity of killer T cells.
The response of B lymphocytes to a foreign _________, clonal _____ and the release of ______clonal antibodies (the humoral response).
The response of B lymphocytes to a foreign antigen, clonal selection and the release of monoclonal antibodies (the humoral response).
B cells
-type of white blood cell
-covered in antibodies that bind to antigens to form and antigen-antibody complex
-each b-cells has a differnt shaped antibody on its membrane, so each binds to a differnt antigen
1) antibody on the surface of the b-celll attches to the ________ antigen, the antigens enters the cell by endocytosis and gets presented on its surface.
2)Th cells bind to these processed antigens and stimulate the B cell to divde by _______ to form a clone of identical B cells (plasma cells), all of which produce the antibody specifc to the forgein antigen
3) this is called clonal ________
1) antibody on the surface of the b-celll attches to the complementary antigen, the antigens enters the cell by endocytosis and gets presented on its surface.
2)Th cells bind to these processed antigens abd stimulate the B cell to divde by mitosis to form a clone of identical B cells (plasma cells), all of which produce the antibody specifc to the forgein antigen
3) this is called clonal selection
what is formed why the antibody binds to the antigen?
antigen-antibody complex
cloned B-cells become….
plasma cells=produce and secrete specifc antibody that exactly fits the antigen on the pathogens surface which destorys it. (primary response)
memory cells= cirulate in blood and tissue fluid in readiness to responsd to future infection of same pathogen by dividing and developing into plasma cell that produce antibodies.
Plasma cells sectrete loads of antibodies specific to the antigen these are called…
monoclonal antibodies
Antibodies
-proteins
-specificity of antibody depends on its variable regions which form antigen binding sites
-each antibody have a varible region with a unique teritary structure thats complementary to a specific antigen
-all have the same constant region
(draw one)
antibody has 2 binding sites……
-so can bind to 2 pathogen antigens at the same time
-pathogens become clumped together=agglutination
-phagocytes then bind to the antibodies an phagocytose many pathogens at once
-this leads to destruction of pathogens carrying this antigen in the body.
plasma cells
-screte antibodies into the blood plasma
-survive only a few days
-produce antibodies
-responsible for the immediate defence of body cells
B memory cells
responsible for secondary immune reponse
-live longer than plasma cells
-dont produce antibodies directly
-when encounter same antigen they divide rapidly into plasma cells and more memory cells
-provide long term immunity
primary response
-when the antigen enters the body form the first time this triggers an immune reponse.
-primary reponse=slow, not many B cells that make te right anitbody to bind to it
-eventually makes enough antibody to overcome infection, in meantine infected person will show symptoms
-after exposure both T and B cells produce memory cells, so can reposn quick to seconf infection
T memory cells vs B memory cells
T- remember specific antigen and will recognise the second time round
B-remeber specific antibodies need to bind to the antigen
secondary response
- if the sam antigen enters the body again the body will produce a quicker and stronger immune response
-clonal slection happens faster
-B memory cells are activated and divide into plasma cells which secret the right anotbody for the antigen
-T memory cells activated and divide into the right type of T cells to kill the cell carrying the antigen
-secondary response often gets ride of the pathogen before you show symptoms
Active immunity
body makes own antibodies after being stimulates by an antigen
active natural
become immune after catching the disease ( specific immune reponse)
active artificial
become a immune after given harmless dose of antigen in vaccine- stimulates immune reponse but doesn’t cause disease
passive immunity
type of immunity you get from being given antibodies made by a different organism
passive natural
baby become immune due to the anitbodies it recive from it mother, though the placenta and in breast milk
passive artificial
become immune when been injected with antibodies from someone else e.g if contract tetnus you can be injected with antibodies against the tetnus toxin,collected from blood donations
active vs passive immunity
-Active immunity requires exposure to the anitgen, passive doesn’t
-active takes a while for protection to devlop, passive protection=immediate
-active memory cells are produced, passive memory cells aren’t produced
-active p;rtection= long term as antibody is produced in response to complementary antogen being presnet ( due to memory cells), protection is short term because the antibodies are broken down
types of vaccine
live (live pathogens)
dead (killed pathogen)
attenuated (weakened pathogen)
toxioids- (toxins made harmless)
DNA
edible vaccines
vaccines
-antigens in avccine cuase body to produce memory cells, against a partcular pathogen WITHOUT the pathogen cuasing disease
-protect people that have them, reduce occurance of disease thoes around them also less likely to get the disease (herd immunity)
Herd vaccination
vaccinating most or all people
stops infection spreading within the population
ring vaccination
vaccinate all people around the infected person, contains the spread within the ring-stops tranmission,trace and isolate contacts, travel restriction
vaccines useually contain _____ these may be free or attached to a dead or ______ pathogen. can be injected or take orally.
vaccines useually contain anitgens these may be free or attached to a dead or weakened pathogen. can be injected or take orally.
disadvantages of taking vaccine orally
-could be broken down by enzyme in gut
-molecules in vaccine could be too large to be absorbed into the blood
successful vaccination
-few side effects
-means of mean of administering the vaccine properly at the appropriate time
-must be possible to vaccinate vast majority of vunerable people to produce herd immunity
-means of produing storying and transporting must be availble
-economically availble in sufficent quanitities to immunise most of vunerbale population
why may vaccination fail to elminate disease?
just a few..
-may fail to induce immunity in some indivivduals
-pathogen may mutate frequently
-indiviudals may object to vaccination for religous or ethical reasons, or medical
ethical issues of vaccines
-all vaccines tested on animals
-animal base substance may be used to produce the vaccine
-tesing vaccine on humans may be risky ( put them selves at unecessary risk of contracting as belive to be fully protected)
-risk of sideeffects
-if epidmic and rush to reicve vaccine diffucult decision as to who recieves first have to be made
monoclonal antibodies
-produced from a single group of gentically identical B cells (plasma)
-all identical in structure
monoclonal antibodies in anti cancer drug targeting cancer cells
1) cancer cell have antigens-called tumour markers not found on normal body cells.
2)monoclonal anrtibodies that bind to the tumor makers can be made
3)anticancer drugs can be sttached the antibodies which will bind to the tumour markers and block chemical signal that stimulate uncontrolled cell growth
4)so drug will only accumlate in body where there are cancer cells, so side affected of antibody-based drugs less than other as only accumlate near specific cells.
Monoclonal antibodies is medical diagnosis
used for diagnoses of influenza,hepatitas,chlamydia infections and certain cancers.
monoclonal antibodies in pregnancy tests
pregancy tests decect hormone hCG which is found in urine of pregnat women
1)application area contains antibodies that are complementary to the hCG prteins bound to a coloured bead (blue)
2)when applied to the application area any hCG in the urine will bind to the antobody on the beads forming and antibody-antigen complex
3)urine moves up the strip carrying the beads with in
4)test strip contains antibodies to hCG which are immobilised (stuck in place)
4)if there is hCG present test strip will turn blue as immobilised antibody binds to the hCG- this concerntates the hCG- antibody complex with the blue bead attached
if hCG not presnt there will be no colour change as the beads willl pass through the test strip without binding to anything
The ELISA test
-enzyme-linked immunosorbant assay
-allows to see whether a patient has an antibody to any antigen or and antigen to any antibody
-can be used in medical diagnoses to test for pathogenic infections,allergies-almost anything you can make an anitbody for
-
how does the ELISA test work
-an antibody with enzyme attached used .
-enzyme can react with a substrate to produce a coloured product
-causes the solution in the reaction vessel to change colour
-if colour change demonastates antibody or antigen being tested for is present in the sample
-in some ELISA tests quanity of antibody/ antigen can be identified by the intensity of the colour chnage
-there are direct and indirect ELISA tests
HIV structure
-virus particle has a spherical structure
-core containing genetic material (two copies of mRNA) and some proteins (including some reverse transcriptase needed for viral replication)
-outer coating protein called a capsid
-an extra outer layer called an envelope (made from the membrane from previous host cell, consits of glycoproteins and lipid bilayer)
-attchment proteins=glycoproteins = gp120 molecules
-sticking out out from the envelope are lots of attachment protein help HIV attach to host helper T-cell
antigenic variation
where pathogens change their antigens
(different antigens are formed as a result of changes in the genes of the pathogen)
why can antigenic variation cause you to be ill again, if infected with the same pathogen
-memory cells from first infection will not recognise the anitgens
-primary response aginst these antigens has to be carried out
-this takes time, which is why symptoms develop and you become ill again
antigenic variation affect on vaccines
-makes it hard to develop vaccine against some pathogens
-examples of pathogens that show agentic variation are HIV and influenza virus
HIV can only _____ inside cells of an organism. HIV replicates inisde helper _ cells pf host. It doesn’t have the equipment to replicate on its own so it uses thoes of the host cell
HIV can only reproduce inside cells of an organism. HIV replicates inisde helper T cells pf host. It doesn’t have the equipment to replicate on its own so it uses thoes of the host cell.
how HIV replicates
1)attcahment protein attches to recpetor molecule (CD4 receptors) on the cell membrane of host helper T cells, virus envelope fuses with cell surface membrane.
2)capsid relased into cell, where it uncoats and release geneti,c material (RNA) into cells cytoplasm
3)Reverse transriptase (enzyme for reverse transcription) used to make complemntary strand of DNA from viral RNA template
4) from this doubke stranded DNA is made and inserted by intergrase (enzyme) into human DNA
5)host cell used to make viral proteins from viral DNA found in human DNA
6)viral proteins assembled into new viruses, which bud fromt he cell and go to infect other cells
why is HIV called a retro virus
uses reverse transcription to replicate
Host killer T cells recognise and destroy heavily infected helper T cells….
- results in a reduction of helper T cells, meaning activation of many macrophages and T killer cells doesn’t take place
-therfore, normal functioning of T helper cells is lost/ reduced
-leaving the idividual vunerable to secondary infection
Factors that affect the progression of HIV into aids
existing infections
strain of HIV
age
access to healthcare
AIDs
acquired immune deficiency virus
condition where immune system deteriates and ecentually fails, makes thoes with it more vunerable to infections
why antibiotics don’t work for viruses
1) antibitics kill bacteria by interfering with metabolic reactions
2)bacterial enzymes and ribosome=diff to humans. antibiotic deigned to target bacterial only os don’t damage human cells
3)viruses don’t have own enzymes and ribosomes-use host cells. antibiotics can’t inhibits them as they dont target human processes
4|) most antivrial drus are deigned to target the few virus-specifc enzymes. e.g HIV uses reverse transcriptase to repliacte, humans celjls dont use this enzyme so drugs can be designed to inhibit without affecting host cell. reverse transcriptase inhibitors.
Is there a cure or vaccine for HIV
no but antiviral drugs can be used to slow the progression of HIV infection and AIDs in an infected person
symptoms of HIV
.1week-10days after HIV infection symptoms can occur, a result of the body reacting to the infection
-most common symptoms= severe flu like symptoms,sore throat,fever,raash on chest,fatigue,nausea,diarrhoea
4 main stages of HIV
1)acute HIV syndrome
2)asymptomatic chronic stage
3)symptomatic disease
4)advanced AIDs
how is HIV passed on
infected blood,semen,vaginal fluids,rectal secretions or breast milk
treatments
-education
-work on developing vaccines is limited
-drug therapy, antiviral drugs which stimulates the immune system
Direct ELISA test
-uses a single antibody for the antigen you are testing for
-antigens from patient sample bound to inside of a well in a well plate.
-detection antibody attached to enzyme, that is complementary to antigen of interest is added.
-if antigen of interest present will be immobilised on the inside of the well and the detection antibody will bind to it
-well washed out to remove any unbound antibody and substrate solution is added
-if antibody is present the enzyme reacts with substrate =colpur change
-this is a pos result for presence of the antigen
The indirect ELISA test
-uses 2 different antibodies
e.g indirect elisa test can be used to see if patient has antibodies for HIV:
1)HIV antigen bound to bottom of well in well plate
2)sample of patient blood plasma is added. if there any HIV specific antibodies in the sample they will bind to the antigens stuck on the bottom of the well. well is washed to remove any unbound antibodies
3)secondary antibody with specific enzyme attached is added to the well, this will bind to the HIV specific antibody (primary antibody). well washed put to remove any unbound secondary antibody. if no primary antibody presnt all secondary antibody will be washed out as there’s nothing to bind to
4.substrate solution added,reacts with enzyme attached to secodnary antibody to produce coloured product, colour change means pateint has HIV antibodys and is infected with HIV (colour change pos result)
ethical issues of using monoclonal antibodies in medicine
-mice used to produce monoclonal antibodies
-informed consent need by pateins-have been some deaths assciated with their use in treatments of MS
-testing new drugs presents certain dangers (health issues associated to drug trials.)
