Immune response Flashcards
Pathogens are
disease-causing microorganisms
Pathogens can infect both
plants and animals
Bacteria
They reproduce rapidly and can affect the host by releasing toxins, these damage tissues and make us feel unwell.
Viruses
They need a host to survive and reproduce
Fungi
They grow on living tissue, some are single-celled and others have a body made of hyphae.
Protists
Eukaryotic organisms. Some of them are parisitic, that live on or inside the host organism. They are often transferred by vectors.
Direct transmission
- Direct contact such as shaking hands
- sexual contact
- Placental transfer from mother to foetus over the placenta.
Indirect transmission
- vector- organisms that can transfer the pathogen from one host to another
- Droplet infection- droplets of mucus can contain the pathogen are coughed and sneezed out.
- Waterborne and food- the pathogen infects the water or uncooked food and is ingested by the organism.
Prevention methods
- destroying vectors- killing vectors can prevent the spread of certain diseases such as malaria.
- simple hygiene methods- washing hands and using a tissue to sneeze or cough can prevent the spread of disease.
- Isolation and vaccines- Isolation of infected individuals and vaccinations to prevent infections can reduce spread.
Antibiotics are only effective against
bacterial pathogens
How can the spread of malaria be reduced?
1, stop mosquitoes breeding
2, use mosquito nets
3, wear/use insect repellent
Phagocytosis
- Phagocytes engulf and digest pathogens, this can be non-specific or helped by antibodies which cause agglutination (clumping) of pathogens
- The phagocyte surrounds the pathogen and releases enzymes to digest and break it down to destroy it
- tracking pathogen
- binding
- engulfing
Toxins
Tiny poisons that can damage our cells
anti-toxins
small molecules that can bind and counteract the toxins- no damage
Antigen is detected as
foreign
Antibodies
small proteins that are made by our own white blood cells
- can act as signals
- lock on
Each antibody is specific
to an antigen
memory cells
Our body will start to produce so many antibodies so quickly- kill pathogens- immune
What is the role of the immune system once the pathogen has entered the body?
To prevent the infectious organism from reproducing and to destroy it.
How do white blood cells help to defend against pathogens?
- phagocytosis
- production of antibodies
- production of antitoxins (special types of antibody)
Phagocytosis
- Phagocytes engulf and digest pathogens, this can be non-specific or helped by antibodies which cause agglutination (clumping) of pathogens
- The phagocyte surrounds the pathogen and releases enzymes to digest and break it down to destroy it
- antibodies enhance the activity of phagocytes
- antibodies cause agglutination (clumping of pathogens)
- specific antibodies to pathogen produced
Production of antibodies
- Lymphocytes produce antibodies
- Antibodies are Y-shaped proteins – each individual has the potential to make millions of different types of antibodies, each with a slightly different shape
- The aim of antibody production is to produce the antibody that is specific (complementary) to the antigens on the surface of the pathogen
- This is a specific type of immune response as the antibodies produced are specific to each pathogen’s antibodies
- anibodies which have a complementary shape to antigens on a pathogen are produced to enhance an immune response
- each lymphocyte only produces one type of antibody
Why may you feel unwell?
It can take a few days to make the antibodies that are specific to a pathogen and this may give the pathogen causing the infection enough time to make you feel unwell (as its numbers in the body, and consequently the damage caused by them, increases).
Memory cells
-Memory cells are lymphocytes that remain in the body after an initial infection with a particular pathogen; they produce the specific antibodies against its antigens so that if you get infected by the same pathogen again in the future (and the antigens are the same) you can produce antibodies much quicker against it before its numbers increase and it can cause damage to the tissues of the body
Production of antitoxins
- Some pathogens (usually bacteria) can produce substances which act as toxins which make you feel unwell
- Lymphocytes can produce antibodies against these substances – in this case, they are called antitoxins
- The antitoxins neutralise the effects of the toxin
Antitoxin
It is a protein that neutralises the toxins produced by bacteria.
Vaccination
- will prevent illness in an individual by providing artificial immunity
- involves exposing an individual to the antigens of a pathogen in some form, triggering an immune response which results in the formation of memory cells which can make antibodies against it
If a vaccinated individual is infected with the pathogen,
they can destroy it before they become infectious
What do vaccines do?
-vaccines reduce the likelihood that an infected individual will spread the pathogen they have been vaccinated against to others
Herd immunity
-If a large number of the population are vaccinated, it is unlikely that an unvaccinated individual will become infected with the pathogen
Three main scenarios with vaccination
- There are no vaccinations and the disease spreads quickly
- Some of the population are vaccinated and the disease spreads to less people
- Most of the population are vaccinated and this prevents the spread
Wordwide vaccination
- The role of the WHO is to monitor global diseases, they will track if a disease is endemic, epidemic or pandemic
- The importance of vaccines cannot be underestimated:
- The number of people with measles worldwide is increasing even though there is a vaccine
- The increase is due to a drop in the vaccination rate globally – there was some controversy over the MMR vaccine in 1998 and the number of vaccinations dropped significantly after this
- Vaccines have reduced drastically the cases of diseases worldwide
endemic
a disease that is present in a population permanently
epidemic
an outbreak of a disease that attacks many people at the same time and spreads through several communities
pandemic
When an epidemic spreads throughout the world
Advantages and disadvantages of vaccination
Advantages:
- diseases that were once common are now fairly rare due to widespread vaccinations (eg: polio, measles)
- epidemics can be prevented if a large number of the population are vaccinated.
Disadvantages:
-the vaccine doesn’t always give immunity
- there can be side effects of a vaccine, such as a swelling or a rash to more severe reactions such as seizures.
How does a vaccination work?
-Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies
-If the same pathogen re-enters the body the white blood cells respond quickly to produce the correct antibodies, preventing infection
1, harmless pathogen injected
2, Antigens trigger an immune response.It can take days for a lymphocyte making complementary antibodies to be activated.
3, Lymphocyte able to produce complementary antibodies multiplies, antibodies released.
4, Memory cells (lasting years) are produced.If antigen is encountered again, antibodies are produced much faster.
What are the two types of immunity?
- Active immunity that comes from the body creating antibodies to a disease either by exposure to the disease (natural) or by vaccination (artificial)
- Passive immunity that comes from antibodies given to you from another organism, for example in breast milk
When exposed to a virus (eg: measles) naturally and infected,
-an individual can produce a higher concentration of antibodies much more quickly to destroy it
