Vaccines, Disease & Monoclonal Antibodies
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教育者の方へ: Vaccines, Disease & Monoclonal Antibodies(Biology、AQA)向けのすぐ使えるレッスンスライド, 復習ノート — レッスンで使うか、学習者がライブゲームとして遊ぶインタラクティブなクラス活動としてトピックを実施できます。
レッスンノート
Vaccines
- Vaccines introduce pathogenic antigens into the body, triggering a specific immune response and antibody release by plasma cells.
- They may contain weakened pathogens, antigens, or genetic material coding for antigens.
- Vaccination produces active immunity because it causes memory cells to form.
- On later exposure, memory cells give a faster, stronger secondary response that eliminates the pathogen before symptoms develop.
- Vaccines protect both individuals and populations by triggering immunity.
Herd Immunity
- Herd immunity occurs when enough people are vaccinated to stop the spread of infection.
- It protects unvaccinated individuals, such as babies or those with weakened immune systems.
- The more infectious a disease, the higher the proportion of the population that must be vaccinated.
- If vaccination rates drop below the threshold, herd immunity is lost (e.g. measles outbreak in Swansea, 2012).
- Herd immunity reduces the number of susceptible individuals and halts the spread of infection.
Active & Passive Immunity
- Active immunity occurs when the immune system is stimulated by an antigen to produce antibodies and memory cells.
- It can be gained naturally from an infection or artificially from a vaccination.
- Active immunity provides long-term protection due to memory cell formation.
- Passive immunity is when a person receives ready-made antibodies without producing them.
- No immune response is triggered, so no memory cells form and protection is short-term.
- Passive immunity is useful when immediate protection is needed, e.g. tetanus antitoxin.
- Passive immunity can be artificial (injection of antibodies) or natural (via placenta or breast milk).
HIV Structure and Replication
- HIV is a retrovirus with RNA as its genetic material.
- It contains reverse transcriptase, which converts viral RNA into DNA.
- It has a protein coat (capsid), a lipid envelope derived from the host cell membrane, and attachment proteins.
- HIV is transmitted by direct exchange of body fluids, e.g. during sexual intercourse or blood donation.
- Replication: viral RNA enters the helper T cell; reverse transcriptase makes a DNA copy; the DNA inserts into the host chromosomes; viral proteins are produced; new HIV particles are assembled and released, killing the helper T cell.
- New HIV particles infect other helper T cells, gradually reducing their number.
AIDS
- HIV infection often causes mild flu-like symptoms initially, followed by a latent period with no obvious symptoms.
- Over time, HIV becomes active and destroys helper T cells.
- Fewer helper T cells means B cells are no longer activated, so no antibodies are produced.
- This weakens the specific immune response, reducing the ability to fight infections.
- Eventually the person develops AIDS (acquired immune deficiency syndrome).
- Opportunistic infections (e.g. TB) can then occur and may be fatal.
- There is no cure for AIDS, but antiviral drugs can slow virus replication; with treatment, HIV-positive individuals can have a normal life expectancy.
- Antibiotics are ineffective against viruses like HIV because viruses lack metabolism and the cellular structures targeted by antibiotics.
Monoclonal Antibodies
- Monoclonal antibodies (mAbs) are identical antibodies from a single B cell clone.
- They are highly specific and bind to one particular antigen.
- In drug delivery, mAbs can be designed to bind only to specific cells, e.g. cancer cells, carrying a therapeutic drug directly to them.
- This increases effectiveness and reduces damage to healthy cells.
- In medical diagnosis, mAbs detect the presence and location of specific antigens and are often labelled with a radioactive, fluorescent or enzyme marker.
- Common uses include pregnancy tests (hCG), infection detection (e.g. HIV, Streptococcus), cancer screening and locating blood clots/tumours.
ELISA
- ELISA (Enzyme-Linked Immunosorbent Assay) uses antibodies to detect the presence and quantity of a specific antigen or antibody in a sample.
- An enzyme is attached to antibodies; when the enzyme reacts with a substrate, a coloured product forms.
- A colour change indicates that the antigen or antibody of interest is present.
- Direct ELISA uses a single antibody complementary to the antigen being tested for.
- Indirect ELISA uses two antibodies: primary and secondary.
- In indirect ELISA for HIV: HIV antigens are fixed to the well; patient plasma is added; HIV-specific antibodies bind; wells are washed; enzyme-linked secondary antibodies are added; another wash removes unbound antibodies; substrate is added; a colour change indicates the patient has HIV-specific antibodies.
Ethical Issues with Vaccines & Monoclonal Antibodies
- Vaccines are first tested on animals, which some view as unethical; animal-derived substances may also be used in production.
- Human testing carries risks (e.g. side effects or false sense of protection); volunteers may be vulnerable if motivated by payment.
- Some avoid vaccines due to small risk of side effects; herd immunity protects them, which some argue is unfair.
- Concerns over parents refusing vaccines for children, potentially putting them at risk.
- During epidemics, questions arise over priority groups (e.g. elderly or healthcare workers during COVID-19) and global inequality in access.
- Monoclonal antibodies: mice are used to produce mAbs, raising animal welfare concerns.
- mAbs may have serious side effects; informed consent is essential, and trials may involve vulnerable participants.
- mAb treatments are often expensive, raising concerns about fair access, especially in lower-income countries.
Evaluating Studies: The MMR Vaccine Example
- The MMR vaccine protects against measles, mumps, and rubella.
- A 1998 study based on just 12 children suggested a link between the vaccine and autism.
- It was later revealed that one author had a conflict of interest (consulting for parents suing vaccine manufacturers).
- The study was discredited and retracted, but caused a drop in vaccination rates.
- A 2005 study of 30,000 children in Japan showed autism rates continued to increase even after the MMR vaccine was stopped.
- This suggests no link between the MMR vaccine and autism; the large sample size increases confidence in the results.
- Key evaluation points: repeatability, reproducibility, validity, large unbiased sample sizes, peer review, replication, and transparency in funding and conflicts of interest.
スライド
練習問題
無料プレビュー — 59問中8問。すべて見るには登録を。
1.Which of the following best defines a vaccine?
Easy- AA preparation containing antigens that stimulates an immune response and the production of memory cells
- BA preparation containing ready-made antibodies that provides immediate protection
- CA drug that kills bacteria by disrupting their metabolism
- DA substance that directly destroys pathogens in the blood
2.What name is given to the level of immunity in a population that stops a disease from spreading?
Easy- AActive immunity
- BPassive immunity
- CHerd immunity
- DNatural immunity
3.Which of the following is an example of natural passive immunity?
Medium- AAntibodies passing from mother to foetus across the placenta
- BBeing vaccinated against measles
- CRecovering from a chickenpox infection
- DReceiving an injection of antivenin after a spider bite
4.Which of the following correctly describes a difference between active and passive immunity?
Medium- AActive immunity produces memory cells, whereas passive immunity does not
- BPassive immunity produces memory cells, whereas active immunity does not
- CActive immunity provides immediate protection, whereas passive immunity takes 1–2 weeks
- DPassive immunity lasts a lifetime, whereas active immunity is short-term
5.Which enzyme does HIV use to convert its RNA into DNA?
Medium- AReverse transcriptase
- BDNA polymerase
- CRNA polymerase
- DLigase
6.Why are antibiotics ineffective against viruses such as HIV?
Medium- AViruses lack the cellular structures and metabolism that antibiotics target
- BViruses are too large for antibiotics to penetrate
- CViruses have a protein coat that antibiotics cannot break down
- DViruses replicate too quickly for antibiotics to act
7.What is a monoclonal antibody?
Medium- AAn antibody produced by a single clone of B cells that binds to one specific antigen
- BA mixture of antibodies that bind to many different antigens
- CAn antibody produced by the body in response to a vaccine
- DA type of white blood cell that engulfs pathogens
8.In an indirect ELISA test for HIV, what is the purpose of washing the well after adding the patient's blood plasma?
Medium- ATo remove unbound antibodies
- BTo remove bound antibodies
- CTo add the substrate
- DTo attach the enzyme to the antibodies
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