Cell Recognition And The Immune System Flashcards

Question

how can t lymphocytes recoginse and respond to specific antigens

Answer 1

the t cell receptors have a very specific shape active site which can only bing to a specific antigen

Answer 2

Th cells - helper cells Tc cells -cytotoxic cells Ts cells- supressor cells Tm cells - memory cells

Answer 3

when presented to an antigen they release chemicals called cytokines which activate phagocytic macrophages activate other types of cell activate B cells which then go on to produce antibodies

Answer 4

they kill cells displaying specific antigens

Answer 5

regulate the immune response

Answer 6

provides immunological memory and facilitates rapid secondary responses to infection

Answer 7

- foreign antigens are present to activated t lymphocyte -specific receptor on surface of t cell combines/ binds to antigen as it has complementary shape - t lymphocyte is stimulated to divide rapidly by mitosis producing many genetically identical cells-clonal expanison -specific t cells then divide into the 4 types of t cell

Answer 8

B-lymphocytes (B cells) remain in the bone marrow until they are mature and then spread through the body, concentrating in lymph nodes and the spleen Millions of types of B-lymphocyte cells are produced within us because as they mature the genes coding for antibodies are changed to code for different antibodies

Answer 9

-antigen enters the blood/ tissue fluid and comes into contact with an inactive b cell with complementary antibody attached on CSM -antigen binds to surface of antibody and the b cell is stimulated to engulf the antigen - t helper cell bind to displayed antigen and produces cytokines - the cytokines activate the b cell to divide by mitosis producing genetically identical cells that produce the same type of antibody -most of these cell form plasma cells which live in the body for a few days and produce large amounts of the specific antibody which then destroy the pathogen by steps 1-4 - primary response - the rest of the cell become memory cells which can live in body for many years and respond quickly if they come into contact with the antigen again- by producing large quantities of antibody- secondary response

Answer 10

extremely well-developed endoplasmic reticulum which can produce antibodies at a rated of 2000 molecules per second

Answer 11

Immunoglobulin proteins that are produced by b cells and are specific to a particular antigen

Answer 12

4 chains - 2 longer heavy chains and 2 light shorter chains with two binding sites

Answer 13

disulfide bridges - creates a hinged region that makes the molecule flexible

Answer 14

the variable region- it is specific to each individual antibody due to different AA sequence which results in a different tertiary structure

Answer 15

the constant region

Answer 16

agglutination neutralisation of toxins precipitation lysis

Answer 17

forms antibody-antigen complex-An antigen and its complementary antibody have complementary molecular shapes This means that their molecular structures fit into each other When an antibody collides (randomly) with a foreign cell that possesses non-self antigens with a complementary shape, it binds with one of the antigens

Answer 18

bacterial cells clump together with the antibody forming a complex which is easier to phagocytose

Answer 19

complemantary antiboides combine with toxin molecules that are produced by the pathogen and prevent them from binding with the surface of body cells

Answer 20

antibodies attach to soluble antigens causing them to precipitate out of the solution- they are then destroyed by phagocytosis

Answer 21

Ab-Ag complexes activate a series of blood protiens called complement which bind to the complex and destroy it

Answer 22

After clonal selection and expansion, the B-lymphocytes that have become plasma cells secrete lots of antibody molecules (specific to the antigen) into the blood, lymph or linings of the lungs and the gut These plasma cells are short-lived (their numbers drop off after several weeks) but the antibodies they have secreted stay in the blood for a longer time The other B-lymphocytes become memory cells that remain circulating in the blood for a long time This response to a newly encountered pathogen is relatively slow

Answer 23

If the same antigen is found in the body a second time, the memory cells recognise the antigen, divide very quickly and differentiate into plasma cells (to produce antibodies) and more memory cells This response is very quick, meaning that the infection can be destroyed and removed before the pathogen population increases too much and symptoms of the disease develop This response to a previously encountered pathogen is, relative to the primary immune response, extremely fast- the person has acquired immunity

Answer 24

the time between infection and significant antibody production

Answer 25

antigen comes into contact with b cell activate b cell b cell divides by mitosis production of antibody by plasma cells

Answer 26

Natural active immunity artificial active immunity natural passive immunity artificial passive immunity

Answer 27

develops following natural exposure to an antigen memory cells develop to produce long lasting immunity

Answer 28

immunity develops after exposure to an antigen via vaccination mem cells produce long lasting immunity

Answer 29

transfer of antibodies from mother to baby via placenta and breast milk no mem cells develop and short term immunity

Answer 30

injection with ready made antibodies non mem cells develop and short term immunity

Answer 31

intro of ready made antibodies into an individual to establish immediate protections against a pathogen- short term immunity

Answer 32

deliberate intro of an antigen into body w intention of stimulating a primary response so that secondary response occurs rapidly eliminating the pathogen before it can cause disease

Answer 33

live but attenuated(weakened) form of the pathogen eg polio,measles dead pathogen eg whooping cough modified toxins form casual; pathogen eg tetanus and diptheria purified antigen eg flu harmless bacteria or yeast that have been genetically modified to carry antigens of vaccine eg hepatitis b vaccine

Answer 34

Highly effective with one vaccination giving a lifetime’s protection (although less effective ones will require booster / subsequent injections) Generally harmless as they do not cause the disease they protect against because the pathogen is killed by the primary immune response

Answer 35

People can have a poor response (eg. they are malnourished and cannot produce the antibodies – proteins or their immune system may be defective) and it could be weakened eg elderly Antigenic variation – the variation (due to major changes) in the antigens of pathogens causes the vaccines to not trigger an immune response or diseases caused by eukaryotes (eg. malaria) have too many antigens on their cell surface membranes making it difficult to produce vaccines that would prompt the immune system quickly enough Antigenic concealment – this occurs when the pathogen ‘hides’ from the immune system by living inside cells or when the pathogen coats their bodies in host proteins or by parasitising immune cells such as macrophages and T cells (eg. HIV) or by remaining in parts of the body that are difficult for vaccines to reach (eg. Vibrio cholerae – cholera, remains in the small intestine) some ethically object to vaccines out of fear or just being a fucking arse

Answer 36

have to have few side effects have to make large quantities economically adequate means of storing,transporting and administering it

Answer 37

Herd immunity arises when a sufficiently large proportion of the population has been vaccinated (and are therefore immune) which makes it difficult for a pathogen to spread within that population Those who are not immunised are protected and unlikely to contract it as the levels of the disease are so low It is very important as it allows for the individuals who are unable to be vaccinated (e.g. children and those with weak immune systems) to be protected from the disease The proportion of the population that needs to be vaccinated in order to achieve herd immunity is different for each disease If vaccination rates fall below the required level then herd immunity can break down

Answer 38

they are produced from a specifc clone of b lymphocyte have a highly specific antigen binding site and can only recognise and bind to a very unique and specific antigenic sequence.

Answer 39

A mouse (or another mammal) is injected with an antigen. The antigen may be a vaccine, and it may be injected several times. This causes an immune response in the mouse i.e. corresponding antibodies are produced by B cells. Spleen cells which are responsible for producing the lymphocytes are removed from the animal. The spleen produces B cells which are responsible for the antibody production. These spleen cells are removed from the mouse via a small operation. The spleen cells are fused with tumour cells to form hybridoma cells. The mouse’s spleen cells are fused with myeloma cells (cancerous white blood cells from humans), forming hybridoma cells. The hybridoma cells continuously produce monoclonal antibodies. These hybridoma cells have both the properties of the lymphocytes and tumour cells i.e. they are able to divide indefinitely and produce many monoclonal antibodies. These cells are checked and grown in culture in the lab. The monoclonal antibodies are harvested. The monoclonal antibodies produced by the hybridoma cells can be separated and harvested for further use.

Answer 40

they have the characteristics of both the antibody and tumor - so can divide rapidly and effective in the immune response

Answer 41

using genetically modified mice that have human DNA in them so the body does not respond to the antibody as foregin

Answer 42

Monoclonal antibodies can be used diagnostically for: Pregnancy tests Diagnosing HIV Detecting the presence of pathogens such as Streptococcus bacteria Distinguishing between Herpes I and Herpes II Blood typing before transfusions and tissue typing before transplants Detecting the presence of antibiotics in milk Detecting cancer cells

Answer 43

cancer cells display abnormal antigens (prescise tertairy structure) and the MA produced is very specific so is complementary and bind to cancer cell

Answer 44

-alert the immune system to site and stimulating an immune response (phagocytosis) - eg white blood cells engulf -attach to hormone binding site of the cell so uncontrollable cell division does not occur as hormone cannot bind -can have a specific drug attached which can kill a specific cancer cell -activate complement proteins that punch a hole in the cell causing it to burst -antibody attaches to hormone so it cannot bind

Answer 45

-magic bullet antibody produced against antigen only found on the cancer cell coupled with cytotoxic agent injected into cancer patients and it will only target and kill cancer cells leaving normal cells unaffected

Answer 46

antibody has high affinity and avidity for tumor antigen highly expressed on tumor cell in patient stable in circulation efficiently release the cytotoxin inside the cell drug - needs to be highly potent since only limited number of molecules can attach to the antibody

Answer 47

eg heart disease heart muscle is damaged the myosin - protein- is often exposed the monoclonal antibody is used as a visualiser to see the affected areas of the heart as it binds to the myosin the MA also has a radioactive label which enable sit to be seen on a screen so the surgeon can see the damaged area

Answer 48

Monoclonal antibodies can be used to detect particular antigens in patient samples of blood or tissue. For example, pregnancy testing uses monoclonal antibodies to detect for human chorionic gonadotrophin (hCG). If a woman is pregnant, hCG will be found in urine, so we can do urine tests using monoclonal antibodies. We can use fluorescent dyes when doing tests with monoclonal antibodies. We can evoke colour changes to help us detect positive tests. Refer to the diagram below to understand the following steps: 1. The person urinates. The person gives a urine sample. If they are pregnant, their urine should contain hCG. the hormone has alpha and beta subunits 2. Reaction Site. If hCG is present, it will bind to the free antibody, which has an enzyme attached to it. the antibody beta site is complementary to the hormone beta site so can now carry the dye 3. Test Site. hCG bound to the free antibody (and by extension the dye enzyme) enters the test site. Here, the hCG-free antibody complex will bind to another fixed antibody using the hCG. This will bring the enzyme (attached to the complex) close to a dye substrate – a reaction occurs, causing a colour change. binds to alpha unit 4. Control site. There is fixed antibody in the control site. This will bind to any free antibody (not bound to hCG), and cause a colour change here. If a person is not pregnant, the free antibody moves through the test site, and instead binds to the fixed antibody in the control site, causing a colour change here. If a person is pregnant, the hCG-free antibody complex will form in the reaction site, and this complex binds in the test site, causing a colour change here. Some free antibody will still pass to the control site, so you will see two stripes

Answer 49

disease antigen attaches to dye antibody and begins to move up the paper 1st test line - dye is complementary to the virus - antibody complex - so if present changes line colour 2nd test line (control)- if positive dye moves on to this and there is a change in colour if negative the complex then only moves to control and will bind at control as there is no virus particle on it if not working - no lines

Answer 50

stop the t-cells for carrying out cell-mediated response t-cells will be produced if body thinks new transplant organ is foreign MA deliver a cytotoxic drug which kills the t-cells

Answer 51

Use of animals: All vaccines are tested on animals before they can move onto human-trials (testing on humans) but some people think animal testing is unethical Animal-based substances are sometimes used in the production of vaccines but some people disagree with this Human testing: Even at the human-trial stage, a vaccine carries a small risk (the person being tested on may actually suffer from symptoms of the disease or other, unpredicted side-effects) Volunteers may be at higher risk of contracting the disease if they think the trial vaccine will fully protect them but it actually doesn’t (e.g. they might have unprotected sex because they have had a trial HIV vaccine but they actually end up contracting the disease as a result) Human volunteers are often paid to take part in vaccine trials. Ethical issues can arise if these volunteers feel pressured into doing this (and potentially being harmed in the process due to the reasons described above) because of their financial status (i.e. people who are struggling financially may be more likely to volunteer themselves) Side-effects: Some people refuse to take a particular vaccine due to the (usually very small) possibility of side effects In fact, these people are often protected due to herd immunity. Other people (who have had the vaccination) may think this is unfair Some parents refuse to let their children be vaccinated (for various reasons) but this is ethically questionable - should a parent be allowed to put their child at risk (arguably a much greater risk) of contracting the disease instead? Epidemics: When new pandemics occur (e.g. Covid-19) there is often a struggle as to who should be vaccinated first (e.g. should the elderly be given priority?) There is also often a struggle between countries as to who receives the vaccines first and in what quantities (e.g. poorer countries may not be able to afford as many doses of the vaccine as richer countries - should all countries suffering from a pandemic have equal access to a vaccine?) Ethical issues associated with the use of monoclonal antibodies Ethical issues around monoclonal antibody therapies often revolve around animal rights issues: New monoclonal antibody therapies are often tested on animals before they can move onto human-trials but some people think animal testing is unethical Currently, animals are used to produce the cells from which the monoclonal antibodies are produced but some people think this is an unethical use of animals some people think creating GM mice is unethical - religus grounds

Answer 52

Claims, both negative and positive, are often made about vaccines (e.g. about their success rates or potential side-effects) These claims need to be validated (confirmed) with scientific evidence before they are accepted (i.e. they need to be backed up by scientific research) This often involves other scientists repeating the same study (using the same methodology) and trying to reproduce the results Other scientists may also conduct other studies that try to prove the same theory or find the same results Even then, it is important to evaluate the data used to support claims or new findings concerning vaccines, as well as the methodology behind this data The importance of evaluating data behind claims and new scientific findings also applies to monoclonal antibody therapies and treatments Example: The MMR Vaccine The MMR vaccine is a vaccine against measles, mumps and rubella that is usually given to young children A study published in 1998, the findings of which were based on 12 children with autism, concluded that the MMR vaccine might cause autism. It was later found that one of the doctors who worked in this study was acting as a consultant to some parents of autistic children who were suing the pharmaceutical companies that produced the vaccine Evaluating the study: The study is not very convincing as it had a very small sample size (just 12 children) This increases the likelihood that the results were due to chance The doctor may have been trying to gain evidence for the lawsuit against the vaccine This would make the study biased (a biased person or a biased study favours one side or issue over another) In 2005, a study was published on the incidence of autism in 30,000 children in an area of Japan between 1988 and 1996. The MMR vaccine was first introduced in this area in 1989 but stopped being administered in 1993. Describing the data: The number of children with autism continued to increase even after the MMR vaccine stopped being administered For example, in 1992 (when children were given the vaccine) approximately only 75 per 10,000 children were diagnosed with autism by age 7 but in 1994 (when children were no longer given the vaccine) approximately 200 per 10,000 children were diagnosed with autism by age 7 Drawing conclusions: This study suggests there is no link between the MMR vaccine and autism Evaluating the study: We can have greater confidence in the results of this study (compared to the one in 1998) as the sample size was very large (30,000 children) This improved methodology means that the results are less likely to be due to chance

Answer 53

enzyme-linked immunosorbent assay

Answer 54

ELISA tests can be used to see if a patient has any antibodies to a certain antigen (or any antigens to a certain antibody) For example, they can be used to test for infections by pathogens or for allergies

Answer 55

-monoclonal antibody produced that will bind to a specific target antigen and is placed on the assay plate -sample is added to the well and if antibody is present it will bing due to the specific tertiary structure that is complementary, so will bind to the variable region -plate washed to remove any unbound material -2nd monoclonal antibody is produced and this has an enzyme attached to it - 2nd antibody added to the plate and allowed to attached -plate washed again -plate then flooded with enzyme substrate and a colour change is observed if antibody-enzyme complex if present which in turn means antigen is present

Answer 56

quick and reliable and visual

Answer 57

Human Immunodeficiency Virus is a retrovirus- has the ability to make DNA from RNA due to reverse transcriptase enzyme

Answer 58

The virus is spread by intimate human contact and can only be transmitted by direct exchange of body fluids This means HIV can be transmitted in the following ways: sexual intercourse blood donation sharing of needles used by intravenous drug users from mother to child across the placenta mixing of blood between mother and child during birth from mother to child through breast milk

Answer 59

the HIV virus is made up of several key components: Two RNA strands reverse transcriptase A protein coat (capsid) A viral envelope consisting of a lipid bilayer and glycoproteins The lipid bilayer is derived from the cell membrane of the host helper T cell that the particle escaped from Attachment proteins

Answer 60

When the virus enters the bloodstream it infects a certain type of lymphocyte - helper T cells Normally lymphocytes seek out and destroy pathogens that enter the body, producing antibodies that attach to pathogens and enhancing phagocytic activity HIV avoids being recognised and destroyed by lymphocytes by repeatedly changing its protein coat The virus uses the cell machinery of helper T-cells to multiply: Viral RNA enters the cell Viral reverse transcriptase enzymes produce a DNA copy of the viral RNA The DNA copy is inserted into the chromosomes of the cell Each time the cell divides it copies the viral DNA The infected cells remain normal as the viral DNA is inactive At this stage, the individual is HIV positive and will have antibodies against the virus After a period of time (possibly years) the viral DNA within the host cells becomes active It takes control of the helper T cell More HIV particles are produced This causes the helper T cell to die As a result, thousands of new HIV particles are released which are able to infect other helper T cells Gradually the virus reduces the number of helper T cells in the immune system B cells are no longer activated No antibodies are produced This decreases the body’s ability to fight off infections, eventually leading to AIDS (Acquired immune deficiency syndrome)

Answer 61

Immediately after infection with HIV people often suffer mild flu-like symptoms These symptoms pass and for a period of time infected people might not know they are infected After several months or years, the viral DNA replicated by the HIV virus particles becomes active They gradually destroy and reduce the number of helper T cells present in a host This is detrimental as helper T cells play an important role in the specific immune response They stimulate B cells, the production of antibodies and increased rates of phagocytosis When an individual can no longer produce antibodies they are said to have advanced acquired immunodeficiency syndrome (AIDS)

Answer 62

Do not have bacterial structures/enzymes OR Do not have metabolic processes OR Do not have a cell wall/murein;