Disease and the immune system Module 4 Flashcards
What’s a pathogen and 4 types?
An organism which causes disease, fungi, bacteria, virus and protoctista
What’s a communicable disease?
A disease that can spread between organisms
Tuberculosis affects? and is caused by?
Animals (mainly human and cattle), bacterium
Bacterial meningitis affects? and is caused by?
Humans, bacterium
Ring Rot affects? and is caused by?
Potatoes, tomatoes, caused by bacterium
HIV/AIDS affects? and is caused by?
Humans, virus
Influenza affects? and is caused by?
All animals, virus
Tobacco mosaic virus affects? and is caused by?
Plants, virus
Black sigatoka affects? and is caused by?
Banna plants, fungus
Ringworm affects? and is caused by?
Cattle, fungus
Athlete’s foot affects? and is caused by?`
Humans, fungus
Potato and tomato late blight affects? and is caused by?
Potatoes and tomatoes, protoctisa
Malaria affects? and is caused by?
All animals, protoctisa
What’s direct transmission and 2 examples of it?
When a disease is directly transmitted from one organism to another
eg sexual intercourse passing on HIV and Athelte’s foot can be spread via touch
What’s indirect transmission and 2 examples of it?
When a disease is transmitted from one organism to another via an intermediate
Eg. Potato/tomato late blight is spread when spores are carried between plant via air and then water
Malria is spread between humans via mosquitos
3 factors which affect the transmission of disease?
Overcrowding
Climate
Social factors
How does the skin prevent infection?
Acts as a physical barrier, blocking pathogens from entering the body
Acts as a chemical barrier, by producing chemicals that are antimicrobial and can lower pH, inhibiting the growth of pathogens
How do mucous membranes prevent infection?
These protect body openings that are exposed to the environment, eg. nostrils mouth
Secrete mucus, that traps pathogens, and contains antimicrobial enzymes
How does blood clotting prevent infection?
Mesh of protein caused by platelets, which plugs wounds to prevent pathogen entry, and blood loss
How does inflammation prevent infection?
Triggered by tissue damage, which releases molecules which increase the permeability of the blood vessels causing them to leak fluid into the surrounding area. This causes swelling, and helps to isolate any pathogens which may have entered the damaged tissue
Vasodilation occurs, which increases blood flow to the affected area and brings white blood cells to the affected area and makes it hotter which fights the pathogens
How do expulsive relfexes prevent infection?
Sneeze occurs when the mucous membranes in the nostrils are irritated by things such as dust and dirt
Coughing occurs when there’s irritation in the respiratory tract
Both expel foreign objects from the body, including pathogens from the body
Describe the Physical defences plants have against pathogens?
Waxy cuticle prevents water entering, and staying on there which pathogens could grow in
Plant cells are surrounded by cell walls, which act as protection
Produce a polysaccharide called callose, which gets deposited between plant cell walls and the plasma membrane. It is deposited in times of pathogen invasion, and prevents pathogens entering cells, and can block plasmodesmate, preventing spreading
What chemical defences do plants have?
Produce antimicrobial chemicals, which kill pathogens or inhibit their growth
Produce chemicals which are toxic to insects, reducing insect feeding, and chance of infection via an insect vector
What’s an antigen?
Proteins or polysaccharides found on the surface of cells
What happens when a pathogen invades the body as it’s got a foreign antibody?
Antibody is recognised as foreign, causing an immune response which has non specific and specific stages
What are the 4 stages in the immune response?
Phagocytes engulf pathogens
Phagocytes activate T lymphocytes
T lymphocytes Activate B lymphocytes which divide into plasma cells
Plasma cells make more antibodies to a specific antigen
Describe the first step of the immune response, phagocytes englufing pathogens?
A phagocyte recognises the antigens on a pathogen
The cytoplasm of the phagocyte moves round the pathogen engulfing it
The pathogen is now contained in a phagosome in the cytoplasm of the phagocyte
A lysosome fuses with the phagosome, enzymes digest the pathogen
The phagocyte then presents the pathogens antigens. It sticks the antigens on it’s surface to activate other immune system cells
This is a antigen-presenting cell (APC’s)
What are nuetrophils?
Type of phagocyte, they are the first white blood cell to respond to a pathogen inside the body, and are attracted to cytokines released at the wound
Describe the second step in the immune response, phagoyctes activate T lymphocytes?
A T lymphocyte is another type of white blood cell
Their surface is covered with receptors
The receptors bind to antigens, presented by APC’s
Each T lymphocyte has a different receptor on it’s surface
When the receptor on the surface of a T lymphocyte meets a complementary antigen, it binds to it - so each T lymphocyte will bind to a different anitgen
This activates the T lymphocytes - known as clonal selection
It then undergoes clonal expansion - divides to produce clones of itself
What do T helper cells do?
Release substances to activate B lymphocytes and T killer cells
What do T killer cells do?
Attach to and kill cells that are infected with a virus
What do T regulatory cells do?
Suppress the immune system from other white blood cells
So the hosts own cells aren’t damaged
Describe the 3rd step in the immune response of T lymphocytes activating B lymphocytes which divide into plasma cells?
B lymphocytes are another type of white blood cell, and are covered with proteins called anitbodies
Antibodies bind to complementary antigens to form an antigen-anitbody complex
Each B lymphocyte has a different shaped antibody on it’s surface
This together with other substances from T helper cells, activates the B lymphocyte, causing clonal selection
The activated B lymphocyte then divides by mitosis into plasma cells and memory cells = clonal expansion
Describe the 4th step in the immune response of plasma cells making more antibodies to a specific antigen?
Plasma cells are clones of the B lymphocyte
They secrete lots of the antibody, specific to the antigen into the blood
These antibodies will bind to the antigens on the surface of the pathogen, to form lots of antigen-antibody complexes
Describe the structure of an antibody?
Y shaped
Variable regions at the top, the variable region is complementary to a particular antigen, therefore the region will vary in different antibodies
Hinge region at the bend allows flexibility when the antibody binds to the antigen
The constant regions at the bottom, allow binding to receptors on immune system cells
Disulphide bonds hold the poly peptide chains of the protein together (imagine the Y has been split horizontally down the centre)
3 ways antibodies help to clear an infection?
agglunitating pathogens- each antibody has 2 binding sites, so an antigen can bind to 2 pathogens at the same time, the pathogens become clumped together. Phagocytes then bind to the antibodies and and phagocytose a lot pathogens at once
Neutralising toxins - Antibodies called anti-toxins can bind to the toxins produced by pathogens. Preventing the toxins from harming body cells
Prevent the pathogen binding to human cells - when antibodies bind to the antigens on pathogens, they may block the cell surface receptors that the pathogen needs to bind to the hosts cells. Meaning the pathogen can no longer infect
What is the primary response?
When a pathogen enters the body for the first time, and it’s antigens on it’s surface activate the immune system
Why is the primary response slow and what does this mean?
There aren’t many B lymphocytes that can make the antibody needed to bind to it, eventually there will be enough but during that time the person will show symptoms of the disease
What occurs in the primary response that makes the secondary response much faster?
After being exposed to an antigen, both T and B lymphocytes produce memory cells, which will remain in the body for a long time. So the person is now immune
What occurs in the secondary response and why is it so fast?
When the same pathogen enters the body again
Clonal selection is much faster, memory B lymphocytes are activated, and divide into plasma cells that produce the right antibody for the pathogens antigen
Memory T lymphocytes are activated, and divide into the correct type of T lymphocytes to kill the cell carrying the antigen
Normally gets rid of disease before showing symptoms
How do you spot red blood cells on a smear?
No nucleus, and there is lots of them
How do you spot neutrophils on a smear?
White blood cell, 3 interconnected blobs and cytoplasm is grainy
How do you spot a lymphocyte on a smear?
Smaller than a neutrophil, and the whole cell is nearly taken up by the nucleus
How do you spot a monocyte on a smear?
Type of phagocyte, and it has a kidney bean shaped nucleus, and doesn’t have a grainy cytoplasm
What’s active immunity?
When your immune system makes it’s own antibodies after being stimulated by an antigen
What’s Natural active immunity?
When you become immune after catching a disease
What’s Artificial active immunity?
When you’ve become immune, after you’ve been given a vaccination
What’s passive immunity?
When your given antibodies by a different organism
What’s natural passive immunity?
When a baby becomes immune due to the antibodies it receives from it’s mother , through the placenta, and in breast milk
What’s artificial passive immunity?
When you become immune, after being injected with antibodies from someone else
Differences between active and passive immunity?
Active requires exposure to the antigen, passive does not
In active immunity it takes a while for protection to develop, in passive it’s immediate
In active immunity it’s long term, in passive it’s short term
In active memory cells are produced, but in passive they are not
What’s an autoimmune disease?
When an organism’s immune system, can’t recognise self antigens on it’s own cells, so an immune response is launched on it’s own tissues
What does a vaccination do?
Contains antigens, that causes your body to produce memory cells against a particular pathogen, without the pathogen causing disease. So become immune without experiencing any symptoms
What’s herd immunity?
When the disease won’t spread as most of the population has been vaccinated
Why does a new vaccine need to be made every for the influenza virus?
Because it changes every year so will have new antigens, that the old memory cells won’t recognise
What do antibiotics do?
Treat bacterial infections, without damaging the human body cells
What is antibiotic resistance and why is it a big problem?
When genetic mutations make a bacteria immune to an antibiotic, so it will live and reproduce more passing the allele on to the next generation
The more we use antibiotics, the more superbugs will be created
Example of antibiotic resistant bacteria?
MRSA- causes serious wound infections, and is resistant to methicillin
Why do we need to preserve animals plants and microorganisms in terms of medicine?
They can provide many cures
2 new technologies coming to medicine?
Personalised medicine- doctors will prescribe a medicine tailored to your DNA
Synthetic biology- can make artificial proteins and cells
