12.3 Immunity (Cambridge (CIE) O Level Biology): Flashcards
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- FrontActive Immunity
Define active immunity.
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Define active immunity.
Immunity gained by making your own antibodies and memory cells in response to an antigen.
What two things does the body make during active immunity?
antibodies
memory cells
What are the two ways in which active immunity can develop?
being infected by a pathogen
being vaccinated
Active immunity involves making memory cells that give a future response to .
Active immunity involves making memory cells that give a future response to infection.
Is active immunity fast or slow acting?
It is slow acting.
How long does active immunity last?
It provides long-lasting immunity.
Why does active immunity last a long time?
Because memory cells are made; they stay in the body and respond quickly if the pathogen returns.
How can active immunity be gained without becoming ill?
Through vaccination, which triggers antibody and memory cell production without causing disease.
During active immunity, lymphocytes make that are specific to a pathogen's antigens.
During active immunity, lymphocytes make antibodies that are specific to a pathogen's antigens.
True or False?
Active immunity is slow acting but long-lasting.
True.
It takes time to make antibodies, but the memory cells produced give long-lasting protection.
True or False?
In active immunity the body is given ready-made antibodies from another person.
False.
That describes passive immunity; in active immunity the body makes its own antibodies.
Define antigen.
A protein on the surface of a cell that is specific to that cell type.
Define antibody.
A protein made by lymphocytes with a shape complementary to a specific antigen.
Which cells make antibodies?
Lymphocytes.
Why can an antibody only bind to one type of antigen?
Its shape is complementary to that antigen only, like two jigsaw pieces fitting together.
Antibodies have a shape that is to the antigen they bind to.
Antibodies have a shape that is complementary to the antigen they bind to.
Define agglutination.
The clumping together of pathogens caused by antibodies.
How does agglutination help to destroy pathogens?
Clumped pathogens cannot move easily, and chemicals signal phagocytes to destroy them.
Why might you become ill the first time you meet a new pathogen?
The initial response to make the right antibodies takes a few days, during which the pathogen can multiply.
What is the role of memory cells?
They retain the instructions for making a specific antibody, so on reinfection antibodies are made quickly and in greater quantities.
On reinfection by the same pathogen, memory cells make antibodies more and in greater quantities.
On reinfection by the same pathogen, memory cells make antibodies more quickly and in greater quantities.
True or False?
Antibodies are complementary in shape to antigens.
True.
The complementary shapes let the antibody bind to its specific antigen.
True or False?
Memory cells give immunity against all pathogens, even ones that change their antigens.
False.
Some pathogens mutate and change their antigens (e.g. the cold virus), so memory cells no longer recognise them.
Define vaccine.
A dead or altered (weakened) form of a pathogen containing specific antigens, introduced into the body.
What does a vaccine contain?
A dead or altered pathogen that carries specific antigens.
Why doesn't a vaccine make you ill?
The pathogen is weakened or dead, so it cannot cause illness, but it can still provoke an immune response.
A vaccine contains a dead or altered pathogen that carries specific .
A vaccine contains a dead or altered pathogen that carries specific antigens.
How do lymphocytes respond to a vaccine?
They produce antibodies that are complementary to the antigens.
What is the role of the memory cells made after vaccination?
They remain in the blood and respond quickly if the live pathogen infects the body later.
Vaccination produces cells that respond quickly if the pathogen is met again.
Vaccination produces memory cells that respond quickly if the pathogen is met again.
Why does vaccination give long-lasting immunity?
Because memory cells are produced that stay in the blood.
What determines the level of protection a vaccine gives to a population?
The proportion of people vaccinated.
True or False?
A vaccine contains a weakened or dead form of a pathogen.
True.
The weakened or dead pathogen carries antigens that trigger an immune response without causing disease.
True or False?
Vaccines only give short-term protection.
False.
Vaccines produce memory cells, giving long-lasting protection.
Does vaccination produce active or passive immunity?
Active immunity, because the body makes its own antibodies and memory cells.
Define herd immunity.
When a large enough proportion of a population is vaccinated that the whole population is protected.
How does herd immunity protect people who are not vaccinated?
With most people immune, there are very few places for the pathogen to breed, so it rarely reaches unvaccinated people.
Herd immunity works when a large enough of the population is vaccinated.
Herd immunity works when a large enough proportion of the population is vaccinated.
What happens if the proportion of vaccinated people in a population drops?
The population is at risk of mass infection, increasing the number of infections and deaths.
What large-scale outbreaks does herd immunity help to prevent?
Epidemics and pandemics.
Why are many vaccinations given to children?
Children are seen regularly by medical practitioners and can be vaccinated early, keeping population immunity high.
A successful vaccination programme led to the disease being eradicated in 1980.
A successful vaccination programme led to the disease smallpox being eradicated in 1980.
Which disease was eradicated by a World Health Organisation vaccination programme?
Smallpox, officially eradicated in 1980.
What is the difference between controlling and eradicating a disease?
Controlling keeps a disease at low levels; eradicating removes it completely.
True or False?
Herd immunity can help to prevent epidemics and pandemics.
True.
When enough people are vaccinated, the pathogen cannot spread easily through the population.
True or False?
Herd immunity only protects the people who have been vaccinated.
False.
It also protects unvaccinated people, because the pathogen has few places to breed and spread.
Why does a fall in vaccination rates increase the number of infections?
People are more likely to meet infected, contagious individuals, so the disease spreads more easily.
Define passive immunity.
A fast-acting, short-term defence gained from antibodies acquired from another individual.
Is passive immunity fast or slow acting?
Fast acting.
How are antibodies passed to a baby before birth?
Across the placenta from mother to fetus.
How are antibodies passed to a baby after birth?
Through breast milk during breastfeeding.
Before birth, antibodies pass from mother to fetus across the .
Before birth, antibodies pass from mother to fetus across the placenta.
After birth, a baby receives antibodies from its mother through .
After birth, a baby receives antibodies from its mother through breast milk.
Why is passive immunity important for a newborn baby?
It protects the baby from infection until it is older and stronger and its own immune system is more responsive.
Why is passive immunity only temporary?
The baby does not make its own memory cells, so the protection does not last.
In passive immunity, does the baby make its own antibodies?
No — the antibodies come from the mother.
True or False?
In passive immunity the body makes its own memory cells.
False.
No memory cells are made, which is why passive immunity is only temporary.
True or False?
Passive immunity gives fast-acting but short-term protection.
True.
The ready-made antibodies work immediately but are not replaced, so protection is short-lived.
Which type of cell does HIV infect?
A type of lymphocyte (a white blood cell).
What is the normal role of lymphocytes?
They seek out and destroy pathogens and produce antibodies.
What does HIV do once inside a lymphocyte?
It uses the cell's machinery to multiply.
HIV infects and destroys a type of white blood cell called a .
HIV infects and destroys a type of white blood cell called a lymphocyte.
How does HIV weaken the immune system?
It reduces the number of lymphocytes and the number of antibodies that can be made.
What condition does HIV infection eventually lead to?
AIDS (Acquired Immunodeficiency Syndrome).
Define AIDS.
Acquired Immunodeficiency Syndrome — the condition caused when HIV severely weakens the immune system.
Why do people with AIDS catch infections a healthy person would fight off?
Their immune system is weakened, so it can no longer deal with pathogens it would normally destroy (e.g. influenza, pneumonia).
HIV reduces the number of lymphocytes and the number of that can be made.
HIV reduces the number of lymphocytes and the number of antibodies that can be made.
True or False?
HIV attacks and reduces the number of lymphocytes in the immune system.
True.
With fewer lymphocytes, the body makes fewer antibodies and cannot fight infections well.
True or False?
HIV strengthens the immune system.
False.
HIV weakens the immune system by destroying lymphocytes.
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