Immune System- Abhay Flashcards
what are the main pathogens and give examples of diseases they cause
bacteria – tuberculosis (TB), bacterial meningitis, ring rot (potatoes, tomatoes)
virus – HIV/AIDS (human), influenza (animals), Tobacco Mosaic Virus (plants)
protoctista – malaria, potato/tomato late blight,
fungi – black sigatoka (bananas), ring worm (cattle), athlete’s foot (humans).
How to viruses damage host cells
Viruses insert their genetic material into the hosts cells DNA. They then use the host cell to reproduce.
How do Protoctists damage host cells
Protoctists take over cells and burst them open as a new generation emerge, they do not take over the DNA of the cell but just use the cell contents to reproduce.
How do fungi damage host cells
Fungi digest and destroy cells which they use to reproduce.
They also release toxins that break down cell membrane and inactivate enzymes
How do bacteria damage host cells
Most bacteria and some fungi produce toxins which break down the plasma membrane of the host cell and inactivates enzymes
What type of disease do bacteria cause and give a brief outline of what they do.
Ring Rot; damages plant tubers and leaves. A field cannot be used to grow plant for at least another 2 years.
Tuberculosis; damages and destroys lung tissue and suppresses immune system in animals.
Bacterial Meningitis; bacterial infection of the brain which can spread to the blood quickly causing blood positioning and potentially death
What type of disease do Viruses cause and give a brief outline of what they do
Tobacco Mosaic Virus- Damages leaves roots and stems stunting growth and leading to crop loss. There is currently no cure for it.
HIV/AIDs; Damages T-helper cells and gradually breaks down the whole immune system. No cure or vaccine for it yet.
Influenza Virus- Kill the ciliated epithelial cells of the airways leaving them open to secondary bacterial infection.
What type of disease do Protoctists cause and give a brief outline of what they do
Malaria (Plasmodium)- The female Anopheles mosquito is the vector for this. Malaria reproduces in the mosquito and is then transferred to a human when it feeds on their blood. It attacks red blood cells the liver and the brain.
Potato Blight- destroys leaves and tubers causing vast crop loss
What type of disease do fungi cause and give a brief outline of what they do.
Black Sigatoka; Fungus that invades and breaks down leaves causing them to turn black and preventing them from photosynthesising.
Ring Worm- A fungal diseases which attacks animals, it is not harmful but is unsightly and can cause irritation.
Athletes foot; grows on and digests the warm moist skin between toes. Anti-fungal cream is a cure.
What are the direct ways of transmission of a disease in ANIMALS
Touch- Kissing, intercourse, any skin to skin contact
From an animal bite,
open wound or sharing needles
Ingestion- Eating contaminated food e.g. undercooked chicken causes salmonella
What are the indirect way of transmission of a disease in ANIMALS
Inanimate Objects (fomites)- E.g. bedding, socks or clothes can transfer athlete foot.
Droplet infection- Droplets of saliva that leave your mouth when you talk cough or sneeze
Vectors- Usually animals e.g. Mosquitoes, flea rats, water can also be a vector.
What are factors that affect the transmission of a disease in ANIMALS
Overcrowded living or working conditions
Living in poorly ventilated housing
Poor diet
Compromised immune system- e.g. having HIV/AIDS or being on immunosuppressants
Socio-Economic Factors- Lack of access to doctors, low health care worker to patient ratio
What are the direct ways of transmission of a disease in PLANTS
When plants are in direct contact with each other e.g due to overcrowding
What are the indirect ways of transmission of a disease in PLANTS
Soil Contamination- Infected pathogens often leave spores on the ground e.g black Sigatoka spores which can infect the next crop that is grown there
Wind- Spores can be carried by the wind
Water- Raindrops can carry pathogen or irrigation system may be contaminated
Animals- Insects or animals can be vectors of pathogens
Humans- Can transfer pathogens from touch or fomites (clothing)
What are factors that increase transmission of a disease in plants
Plant varieties- That are susceptible to diseases
Monoculture- low genetic diversity means disease can spread rapidly as all crops are susceptible
Overcrowding- increases likelihood of contact
Warm conditions increase the chance of vectors surviving
Climate change- Increased wind and rainfall are vectors for pathogens
What is a pathogen
A disease causing microorganism
What is a vector
Something that carries a pathogen from one organism to another e.g (water/insects)
What is a communicable disease
A disease that can be passed on from one organism to another
What are the physical plant defences against pathogens
Cellulose cell walls- Acts as barrier to individual cells preventing pathogens from getting in
Callose- Is synthesised when a pathogen is detected, this is deposited in plasmodesmata selfing off the site of infection, calls barriers can also be lignified creating a thicker stronger barrier. Callose can also be deposited in sieve tube end walls to prevent the pathogen spreading via the phloem
Self sacrifice- Unlike animals plants do not heal damaged tissue they instead seal it off and sacrifice it as meristem is constantly dividing so organs can be replaced quickly.
What are the chemical defences plants use against pathogens
Producing Insect replants and insecticides e.g citronella or insect toxins
Producing antibiotics e.g. phenols
Producing anti fungal compounds e.g phenols or chitinases (compound which breaks down chitin cell wall of fungi)
Producing general toxin e.g cyanide which is poisonous to most organisms
What are the three main categories of non-specific immune response against a pathogen in Humans
Reflexes and barriers
Blood clotting & wound repair
Inflammation
What are the two physical barriers humans have to pathogens and what reflexes do humans have
The skin is a protective barrier found all around the body, it secretes sebum oils which inhibit the growth of pathogens, and contains many microorganisms which out-compete pathogens
Mucouse membranes, air ways and tracts in the body are often line with mucous membrane which secrets mucus to trap pathogens. Mucus contains phagocytes to digest pathogens and lysozymes which digest bacterial and fungal cell walls.
Expulsive reflexes e.g. coughing and sneezing expel pathogens out of our air ways
What is the function of platelets in blot clotting
Platelets secrete a molecule called thromboplastin which triggers a cascade of enzyme controlled events that results in the formation of a blood clot (fibrinogen forms fibrin which forms the blood clot)
The blood clot forms a tough protective scab which prevents the energy of pathogens
What is the function of serotonin in response to a wound or cut
Release of serotonin causes blood vessels to constrict reducing blood flow to the wound
What are the function of mast cells in the inflammatory response
Mast cells are activated in damaged tissues which release histamine and cytokines
What are the functions of histamines in the inflammatory response
Histamines make blood vessels dilate, increasing the blood flow to the pathogen making the area hotter which prevents pathogens from reproducing
Histamines make blood vessels more leaky/permeable causing blood plasma to leave blood vessels where it is called tissue fluid. Tissue fluid causes swelling
What are the functions of cytokines in the inflammatory response
Cytokines release chemical that attract white blood cells; phagocytes which digest the pathogen
What chemical release causes a fever
How are fevers a defence against pathogens.
When a pathogen enters the body cytokines are released which act on the hypothalamus of the brain causing it to increase body temperature.
This is advantageous as pathogens have an optimum temperature of 37 or below so a temp of above 37 means they reproduce less
Higher temperatures cause the specific immune response to work faster
Outline the whole process of phagocytosis
- Pathogen releases chemical that attract the phagocytes
- Phagocytes recognise the antigen on the pathogens as non-self
- Phagocyte engulfs pathogen into a temporary vacuole called a phagosome
- Cell cytoskeleton moves lysosome to the phagosome the lysosome fuses with the phagosome forming a phagolysosome
- The hydrolytic enzymes from the lysosome digest and kill the pathogen
- Digest the pathogen into amino acids/ glucose/ fatty acids
- Which are absorbed by cell cytoplasm
- Phagocytes release cytokines which attract other phagocytes to a site of infection
- Neutrophils are an example of a phagocyte that ingest bacteria at a site of infection
What are the functions of opsonins
Opsonins are chemicals that bind to pathogens making them clump together (agglutinate), so they are more easily detected and ingested by phagocytes
What cells produce antibodies
Plasma cells
(Note: Memory cells do not produce antibodies, they remember the specific antibodies to an antigen and then divide into plasma cells which produce the antibodies)
Describe the structure of an antibody
Antibodies are made up of two heavy (long) polypeptide chains and two (shorter) light chains. The two chains are held together by disulphide bridges
Antibodies have a constant and variable region and a hinge region which provides flexibility allow them to bind to two separate antigens
How do antibodies destroy the pathogen
They work by binding to antigens, forming an antigen-antibody complex, causing the pathogens to agglutinate so they are easily ingested by phagocytes
Pathogens cannot effectively enter or attack host cells when they have antibodies bound to them
What are the functions of anti-toxins
Neutralize toxins released by pathogens e.g bacteria and fungi
Name the different types of T-Cells
T-Helper
T-Killer
T-Regulator
T-memory
Function of T-helper cells
Produce interleukins, which stimulates the activity of B cells.
Stimulates the production of antibodies and other T cells,
Attracts macrophages to ingest antigen-antibody complexes
Contain receptors on their cell surface membrane which are complementary to an APC, therefore they are involved in clonal selection and clonal expansion
Function of T-killer cells
Produce a chemical called perforin which makes holes in the pathogen cell membrane making it freely permeable and killing it
Function of T-Regulatory cells
T-Regulator cells: Suppresses the immune system once a pathogen has been removed form the body preventing an autoimmune response where the immune system starts attacking its own cells.
Function of T-memory cells
T-memory cells: Provide immunological memory, if they encounter an antigen again they divide rapidly into many T-killer cells
Name the different types of B lymphocytes
Plasma cells
B-effector cells
B- memory cells
Function of Plasma cells
Produce Antibodies
Function of B-effector cells
Divide to form many plasma cells
Function of B-memory cells
Provide immunological memory to an antigen, so that if it is encountered again B memory cells will divide into plasma cells causing rapid antibody production
What is the difference between cell-mediated and humoral immunity
Antibodies are not produced in cell mediated immunity, whereas antibodies are produced in humoral immunity.
Cell mediated immunity is mediated by T-Cells, humoral immunity is mediated by antibodies
Outline the process of Cell-mediated immunity
1) Macrophages ingest a pathogen and place its antigens on its own cell surface membrane, as a result the macrophage becomes an Antigen-Presenting-Cell (APCs)
2) T-helper cells contain receptors on their cell-surface membrane that are specific to the antigens on the APCs so they bind to them which activates the T-helper cells stimulating them to divide into my T-cell clones
3) Theses T-cell clones may develop into T-memory cells, T-killer cells or produce interleukins which stimulate the activity of B-cells and the production of antibodies
Function of B-lymphocytes
Involved in clonal selection and expansion
Outline the process of humoral immunity
1) B lymphocytes have antibodies on their cell surface membrane. By chance a B cell with the complimentary antibody to the antigens on a pathogen will bind to it and engulf it. The B cell will then present these antigens on its cell surface membrane and become an Antigen-Presenting-Cell (APC)
2) A T-helper cell has receptor sites on it cell surface membrane so will bind to the Antigens on the B lymphocytes this is Clonal Selection
Interleukins released by the T-helper cell stimulate the B cell to divide
3) The B cell divides in a process called clonal expansion into many B-memory cells and plasma cells
4) Plasma cells produce antibodies to combat the pathogen, this it the primary immune response, as it often takes many days for antibodies to be produced
5) If the same pathogen re-enters the body again then B-memory cells will quickly divide in antibodies this is the secondary immune response. The individual will not get symptoms the second time as they are immune to the pathogen.
What is an autoimmune disease
When the immune system recognises body cells as non-self/foreign
What does rheumatoid arthritis affect
Immune system attacks joints especially wrist, ankles and elbows.
What does lupus affect
Affects skin and joints and causes diseases. Immune system can attack other organs e.g liver or kidney.
What does type 1 diabetes affect
Type 1 diabetes- Immune system attacks insulin secreting beta cells in pancreas.
What is natural active immunity
The production of B and T memory cells after coming in contact with a pathogen, which rapidly produce antibodies to destroy the pathogens before it can cause any disease. This is called natural active immunity, as B and T memory cells are actively producing antibodies.
What is natural passive immunity
Breast-feeding a baby provides it with antibodies protecting it from diseases. This is called natural passive immunity.
What is artificial active immunity
An attenuated (weakened) pathogen is injected into your blood stream in a small dose. This is called a vaccine. Your immune system will recognise the antigens on the pathogen as non-self and trigger the primary immune response which will produce B and T memory cells. This will make you immune to the pathogen and you will not experience any symptoms.
What is artificial passive immunity
For some potentially fatal diseases antibodies are produced in one animal (e.g. a horse) and injected into the blood of humans. This immunity is temporary but can be life saving.
Define epidemic
An epidemic is when a communicable disease spread rapidly at a local or national scale.
Define pandemic
A pandemic is when the same disease spreads to several countries or continents
Why are vaccine important
What is herd immunity
Vaccinations are important to prevent an epidemic or pandemic
Once enough individuals in a population are vaccinated herd immunity is reached and the chance of an outbreak is minimal.
Where are most medicine derived from
Plants or microorganisms
What type of organism is the antibiotic penicillin derived from
A mould (fungus) that produces antibiotics
What is synthetic biology
Combining engineering with genetic biology to produce medicines.
Why is synthetic biology useful
Can be used to produce medicines that are:
Too expensive to manufacture
Too rare
Unavailable
Can also be used to make personalised medicines, as the human genome can be sequenced very quickly. Personalized medicine is the future.
What are the advantages of Perosnalised medicines
More likely to be more effective
Patient less likely to experience negative side effects
Give examples of two organisms that are known to be antibiotic resistant
MRSA and C.difficile are high profile examples of antibiotic resistance as they were widely used in hospitals
How can antibiotic resistance be reduced
Minimising the use of antibiotics and ensuring that all antibiotic courses are completed to prevent the survival and reproduction of resistant individuals
Good hygiene in hospitals to prevent the spread of bacterial infections
Why are scientists becoming worried about antibiotic resistance
This is a problem as scientists are worried antibiotic resistance will cause a spike in deaths as it did so in the past. Consequently scientist are using computer modelling and looking at a range of organisms, e.g. soil microorganisms crocodile and fish, to come up with new antibiotics. Despite this antibiotic resistance is developing at a rate faster than the development of new antibiotics.
Define Parasite (3)
An organisms that lives in host cells
and feed on host cells
and harms the host by causing disease
