Module 4 Section 1: Disease and the Immune System Flashcards
What is a disease
A condition that impairs the normal functioning of an organism
Can affect plants and animals
What is a pathogen
An organism that causes a disease
What are the different types of pathogens
Bacteria
Viruses
Fungi
Protoctista
Prion (don’t need to know)
What is a communicable disease
A disease that can spread between organisms
Diseases caused by bacteria
Tuberculosis (TB)
Bacterial meningitis
Ring rot
Diseases caused by viruses
HIV/AIDS
Influenza
Tobacco mosaic virus
Diseases caused by fungi
Black Sigatoka
Ringworm
Athletes foot
Diseases caused by a protoctist
Potato/tomato late blight
Malaria
Tuberculosis (TB)
Bacterium
Affects animals typically humans and cattle
Caused by bacterium mycobacterium tuberculosis
Damages and destroys lung tissue and suppresses immune system
Curable by antibiotics and preventable by improving living conditions
Bacterial meningitis
Bacterium
Affects humans
Caused by streptococcus pneumoniae or neisseria meningitidis
Affects meninges of the brain (protective membranes of brain surface) which can spread to rest of the body causing blood poisoning (septicaemia)
Cured by antibiotics if delivered early
Ring rot
Bacterium
Affects potatoes, tomatoes
Caused by clavibacter michiganensis
Damages leaves, tubers and fruit
HIV/AIDS
Virus
Affects humans
Pathogen called Human Immunodeficiency Virus
Disease: Acquired Immunodeficiency Syndrome (AIDS)
Destroys immune system so people are vulnerable to other diseases
Passed through exchange of body fluids (sex) and blood (needles)
No vaccine or cure but drugs can slow progress of disease
Influenza
Virus
Affects animals including humans
Caused by orthomyxoviridae spp
Attacks and kills ciliated epithelial cells leaving them open to secondary infection
No cure but people can be vaccinated annually
Tobacco mosaic
Virus
Affects tobacco plants, tomatoes, peppers, cucumbers, petunias
Caused by Tomabovirus (?)
Damages leaves, flowers, fruit
Stunts growth and reduces yield
No cure
Black Sigatoka
Fungi
Affects banana plants
Caused by mycophaerella fijiensis
Attacks and destroys leaves turning them black
No cure but fungicide can be used to control spread
Ringworm
Fungi
Affects cattle
Caused by Trycophyton verrucosum
Causes grey-white, crusty circular areas of skin in cattle
Cured using antifungal creams
Athlete’s foot
Fungi
Affects humans
Caused by Tinia Pedia
Grows on and digests warm, moist skin between toes causing cracking and scaling which can be itchy and sore
Cured using antifungals creams
Malaria
Protoctist
Affects animals including humans
Caused by Protoctista plasmodium spread by bites of infected mosquitoes (vector)
Invades red blood cells, liver and brain
No vaccine and limited cures
Potato/tomato blight
Protoctist
Affects potatoes and tomatoes
Oomycete phytophthora
Destroys leaves, tubers and fruit
No cure
How can communicable diseases be transmitted
Directly transmission
Indirectly transmission
How are diseases spread by direct transmission
When a disease is transmitted directly from one organism to another
Can be done through:
Direct contact
Inoculation
Ingestion
How are diseases spread directly by contact
Contact with body fluids of another person
E.g. bacterial meningitis or STIs
Direct skin to skin contact
E.g. ring worm, athletes foot
Microorganisms from faeces transmitted on hands
E.g. diarrhoeal diseases
How can diseases be transmitted indirectly
When a disease is transmitted from one organism via an intermediate
Intermediates include:
Fomites
Droplet infection
Vectors
Examples of disease that can be transmitted indirectly
Potato/tomato late blight is spread when spores are carried between plants - first in the air , then in the water
Malaria is spread between animals via mosquitoes
Mosquitoes act as vectors - they don’t cause malaria themselves, they just spread the Protoctista that cause it
What conditions can affect disease transmission
Living conditions
Climate
Social factors
How can living conditions affect disease transmission
Overcrowded living conditions increase the transmission of many diseases
E.g. TB is spread directly via droplet infection, can also be spread indirectly because the bacteria can remain in the air and infect new people so the risk of infection is increased when lots of people live crowded together
How can climate affect disease transmission
Potato/tomato late blight is especially common during wet summers because the spores need water to spread
Malaria is most common in tropical countries, which are humid and hot
This is because these are the ideal conditions for mosquitoes to breed
How can social factors affect how disease is spread in humans
Risk of HIV infection is high in places where there’s limited access to:
Healthcare: people are less likely to be diagnosed and treated for HIV and anti-HIV drugs are less likely to be available, so the virus is more likely to be passed on to others
Health education: to inform people about how HIV is transmitted and how it can be avoided (e.g. through safe sex practices like using condoms)
How can bacteria be classified
By their shape
By their cell wall
What are the different shapes available for bacteria
Bacillus/ chain of bacilli (rod)
Coccus/ pair, chain or cluster (sphere)
Vibrio (comma)
Spirillum (spiral)
Spirochaete (corkscrew)
How to test for the different types of bacterial cell wall
Gram staining
Different structures of cell wall react differently with the stain
Results of gram staining for bacteria
Gram positive appear purple/blue under light microscope
Gram negative appear red under light microscope
How can different types of cell walls affect how bacteria are treated
The type of cell wall affects how bacteria react to different antibiotics
How do bacteria reproduce
Binary fission
Characteristics of viruses
Protein shell
Genetic information as RNA or DNA
0.02-0.3 micrometers
No organelles
Rapidly evolve
Non living
Always pathogenic
How do viruses replicate
Invade other cells using attachment proteins
Hijack biochemistry of the cell
Insert viral DNA into host DNA
Host cell transcribes and translates viral DNA
Host cell copies viruses
How do the different pathogens damage the body
Viruses: hijack and destroy cells
Bacteria: produce toxins
Protists: digest cell contents
Fungi: saprotrophic feeding and digestion of cells
What are protists
Eukaryotes
Single celled or colonies
Parasitic
Often require vector
Do not fall into any other categories
What are fungi
Multicellular
Fungi can be saprophytes: feed on dead organisms
Fungi can be parasitic: pathogenic fungi which causes disease
Fungi reproduce by making millions of spores which can spread
How do fungi feed
Saprotrophic feeding
Secrete enzymes onto surface of food
Extracellular feeding
Enzymes digest food leaving nutrients
Fungi absorbs nutrients left by enzymes
How to prevent malaria
Preventative measures can be used such as mosquito nets, window and door screens and long sleeves to prevent bites
Preventative measures also include controlling the vector by using insecticides and removing standing water
How are diseases spread directly by inoculation
Through a break in the skin
E.g. during sex (HIV)
From an animal bite
E.g. rabies
Through a wound or through sharing needles
E.g. septicaemia
How are diseases spread directly by ingestion
Taking in contaminated food or drink, or transferring pathogens to the mouth from the hands
E.g. dysentery, diarrhoeal diseases
How are diseases spread indirectly by fomites
Inanimate objects such as bedding, socks or cosmetics can transfer pathogens
E.g. athletes foot
How are diseases spread indirectly by droplet infection
Droplets of saliva and mucus enter the air through talking, coughing or sneezing
If they contain pathogens and are breathed in by people then they can become infected
E.g. influenza, tuberculosis
How are diseases spread indirectly by vectors
Vectors transmit communicable pathogens from one host or another
These are often but not always animals
E.g. mosquitoes (malaria), rat fleas (plague)
Water can also act as a vector of disease
How are plant diseases spread by direct transmission
Direct contact of a healthy plant with any part of a diseased plant
E.g. ring rot, TMV, tomato and potato blight and black sigatoka
How are plant diseases spread by indirect transmission
Soil contamination
Vectors
How is plant disease spread by soil contamination
Infected plants often leave pathogens or reproductive spores from protoctista or fungi in the soil
These infect the next crop
E.g. black sigatoka spores, ring rot bacteria and TMV
How is plant disease spread by vectors
Wind: pathogens can be carried by the wind
Water: spores swim in the surface film of water on leaves
Animals: insects and birds carry pathogens and spores from one plant to another as they feed
Humans: pathogens and spores are transmitted by hands, clothing, fomites, farming practices and through transporting plants around the world
Factors that affect the transmission of communicable diseases in plants
Planting crops that are susceptible to disease
Over crowding plants
Poor mineral nutrition reduces resistance of plants
Damp, warm conditions increase the survival and spread of pathogens and spores
Climate change causing increased rain and wind promotes the spread of disease, changing conditions allow animal vectors to spread to new areas
How do plants recognise and respond to pathogens
Receptors in plant cells respond to molecules from the pathogens or to chemicals produces when the plant cell wall is attacked
The stimulates the release of signalling molecules that switch on genes in the nucleus
This triggers cellular responses such as:
Producing defensive chemicals
Sending alarm signals to unaffected cells to trigger their defences
Physically strengthening cell walls
Physical defences of plants
Waxy cuticles: provide barrier against pathogen entry and stops water containing pathogens from collecting on leaf
Cell walls: physical barrier against pathogens that make it through waxy cuticle
Plant produce callose: makes it harder for viruses to spread and enter cells
Functions of callose
Synthesised within minutes of the attack and is deposited between the cell walls and cell membrane in cells next to the infected cells
These callose papillae act as barriers to prevent the pathogens entering the plant cells around the site of infection
Large amounts of callose continue to be deposited in cell walls after the initial infection
Lignin is added to make the mechanical barrier to invasion thicker and stronger
Blocks sieve plates in the phloem, sealing off the infected part and preventing the spread of pathogens
Deposited in the plasmodesmata between infected cells and their neighbours, sealing them off from the healthy cells and helping to prevent the pathogen from spreading
How do plants use chemicals to defend against pathogens
Plants produce powerful chemicals to either repel insect vectors of disease or kill invading pathogens
How can plant chemical defences be utilised by humans
These chemicals can be used by humans to help control insects, fungi and bacteria
Examples of chemicals used in plant defence
Insect repellants: pine resin
Insecticides: caffeine
Antibacterial compounds (including antibiotics): defensins
Antifungal compounds: chitinases
Anti-oomycetes: glucanases
General toxins: cyanide
How do plants respond to pathogen infection internally
Waxy cuticle thickens
Cell walls get stronger
Guard cells close stomata in the leaf
If microbes are attacking one section of the plant, the surrounding cells self destruct to quarantine the infection
How do animals prevent pathogens getting into the body
Animals have a range of primary, non specific defences to prevent pathogens entering the body
How does skin act as a defence against pathogens
Physical barrier
Blocks pathogens from entering body
Can act as chemical barrier by producing chemicals that are antimicrobial and can lower pH to inhibit the growth of pathogens
Has skin flora of healthy microorganisms that outcompete pathogens for space on body surface
Produces sebum, oily substances that inhibits growth of pathogens
How do mucous membranes act as a defence against pathogens
Protect body openings that are exposed to the environment (e.g. mouth, nostrils, ears, genitals and anus 👅)
Some membranes secrete mucus - sticky substance that traps pathogens and contains lysozymes and phagocytes
How does blood clotting act as a defence against pathogens
Blood clots are a mesh of protein (fibrin) fibres
The clots plug wounds to prevent pathogen entry and blood loss
Formed by a series of chemical reactions that occur when platelets are exposed to collagen from damaged blood vessels
Platelets release:
Thromboplastin: trigger series of reactions resulting in blood clot formation (thrombus)
Serotonin: causes smooth muscle in blood vessel walls contract to reduce blood flow to the area
How does inflammation act as a defence against pathogens
The swelling helps to isolate pathogens that may have entered the damaged tissue
The vasodilation increases blood flow to the area which brings white blood cells to the area to fight off present pathogens
How does inflammation occur
Signs include swelling, pain, heat and redness
Triggered by mast cells in damaged tissue which releases:
Histamines: makes blood vessels dilate causing localised heat and redness, raised temperature helps prevent pathogens reproducing
Histamines make vessel walls leaky so blood plasma is forced out to become tissue fluid (tissue fluid causes swelling and pain)
Cytokines: attract white blood cells (phagocytes) to the site to dispose of pathogens by phagocytosis
How does wound repair act as a defence against pathogens
Skin is able to repair itself in the event of injury and re-form a barrier against pathogen entry
How are wounds repaired
Epidermal cells below scab start to grow to seal the wound
Damaged blood vessels regrow
Tissue below the wound contracts to bring the edges of the wound closer together
Wound is repaired using collagen fibres - too many collagen fibres causes a scar to form
How do expulsive reflexes repair act as a defence against pathogens
E.g. coughing, sneezing, vomiting, diarrhoea
Sneezes happen when the mucous membranes in the nostrils are irritated by dust or dirt
Coughing stems from irritation in respiratory tract
Both coughing and sneezing aim to expel foreign objects, including pathogens, from the body
Happen automatically
Vomiting and diarrhoea expel contents of the gut along with any pathogens
How do tears, urine and stomach act as defence systems
Tears and urine contain lysozymes
Acid in the stomach
Helps prevent pathogens entering the body
How do fevers help kill pathogens inside the body
Normal body temperature is around 37°C and is maintained by the hypothalamus
When pathogens invades the body the cytokines stimulate hypothalamus to increase temperature
Higher temperatures inhibit pathogen reproduction
Specific immune system works faster at higher temperatures
What are phagocytes and how do they kill pathogens
Phagocytes are white blood cells that engulf and destroy pathogens
Two main types: neutrophils and macrophages
Phagocytes build up at the site of infection and attack pathogens
Pus building up in wound is a result of dead neutrophils and pathogens
Stages of phagocytosis
Pathogens produces chemicals that attract phagocytes
Phagocytes recognise non-human proteins on the pathogens
This response is not specific to a type of pathogen, instead it’s against any cell or organism that is non-self
Phagocyte engulfs the pathogen and encloses it in a vacuole called phagosome
Phagosome combines with a lysosome to form phagolysosome
Enzymes from the lysosome digest and destroy pathogen
Difference between neutrophil’s and macrophages’ times to digest pathogens
Neutrophils take under 10 mins to engulf and destroy a bacterium whereas macrophages take longer as they have a more complex process
How do macrophages digest pathogens
When a macrophage has digested a pathogen, it combines antigens from the pathogen surface membrane with glycoproteins in the cytoplasm called the major histocompatibility complex (MHC)
MHC complex moves these pathogens antigens to the macrophage’s own surface membrane
It becomes an antigen presenting cell (APC)
These antigens now stimulate other cells involved in the specific immune system response
What are cytokines and when are they produced
Produced when phagocytes have engulfed a pathogen
They are chemicals that act as cell signalling molecules
Inform other phagocytes that the body is under attack and stimulates them to move to the site of infection or inflammation
Can also increase body temperature and stimulate the specific immune system
What are opsonins
Bind to pathogens and tags them so they can be more easily recognised by phagocytes
Phagocytes have receptors on their cell membranes that bind to common opsonins
The phagocyte then engulfs the pathogen
Different types of opsonins
Many different types
Antibodies such as immunoglobulin G (IgG) and immunoglobulin M (IgM) have the strongest effect
How to examine blood under a microscope
Smear sample
Spreading a drop of blood thinly across the slide
Can be stained to show nuclei of lymphocytes
Identifying the number of different types of lymphocytes in a blood smear indicates if a non specific or specific immune response is taking place
What are T cells
T cells
Mature in the thymus
Have highly specific receptors in their membranes
Respond to ‘changed’ cells (infected cells, antigen-presenting cells, ‘non-self’ cells, mutated cells) - this is the Cell-Mediated Response
Selection of correct T cell leads to expansion by mitosis, then differentiation into variety of T cells (‘T helper’, ‘T killer’, ‘T memory’, ‘T regulator’
T cells play key roles in control and coordination of immune response
What are B cells
B cells
Remain in bone marrow until mature
Congregate in lymph nodes and spleen, forming the ‘humoral response’ - roaming protection in the fluids.
Have highly specific antibodies in their membrane - each B cell can only produce one type of antibody and each B cell is unique.
Selection of correct B cell leads to expansion by mitosis, then differentiation into plasma/effector cells (which produce antibodies) and memory cells.
Different types of T lymphocyte cells
T helper cells
T killer cells
T memory cells
T regulator cells
Different types of B lymphocyte cells
Plasma cells
B effector cells
B memory cells
T killer cells
T killer cells:
Destroy the pathogen carrying the antigen
Produce a chemical Perforin which kills the pathogen by making holes in the cell membrane so it’s freely permeable
T memory cells
T memory cells:
Live for a long time and are part of the immunological memory
If they meet an antigen a second time, they divide rapidly to form a huge number of cloned T killer cells that destroy the pathogen
T helper cells
T helper cells:
Have CD4 receptors on their cell surface membrane which bind to the surface antigens on APCs
Produce interleukins (type of cytokine)
Interleukins made by T helper cells stimulate the activity of B cells, which increases antibody production
Stimulates production of other types of T cells
Attracts and stimulates macrophages to ingest pathogen with antigen-antibody complexes
T regulator cells
T regulator cells:
Suppress immune system, acting to control and regulate it
They stop the immune response once a pathogen has been eliminated
They make sure the body recognises self antigens and does not set up an autoimmune response
Interleukins are important in this control
What are plasma cells
Plasma cells:
Produce antibodies to a particular antigen and release them into circulation
Produced from B effector cells
An active plasma cell lives for a few days but produces around 2000 antibodies per second while it’s alive and active
What are B memory cells
B memory cells:
Live for a long time and provide the immunological memory
They are programmed to remember a specific antigen and enable the body to make a rapid response when a pathogen carrying that antigen is encountered again
What are B effector cells
Divide to form the plasma cell clones
Structure of antibodies
Y shaped glycoproteins called immunoglobulins
Two identical long polypeptide chains called the heavy chains
4 polypeptide chains held together by disulfide bridges
Also disulfide bridges within polypeptide chains holding them in shape
Hinge region of antibody provides flexibility and allows it to bind two separate antigens, one at each of its antigen binding sites
Made up of constant region which is same on all antibodies and allows attachment to phagocytes and contains only heavy chains
Heavy chains extend into variable region which contains light chains and gives specificity
Function of antibodies
Produced by B cells in response to antigens
Bind to specific antigen on pathogen or toxin that has triggered immune response
Bind to antigens with a lock and key mechanism
What is it called when an antibody binds to an antigen
Forms an antigen-antibody complex
Structure of antibody binding site
Area of 110 amino acids on both heavy and light chains
Known as variable region since its different on each antibody and gives them their specificity
How do antibodies defend the body
Antibody in antigen-antibody complex acts as an Opsonins so complex is easily engulfed by phagocytes
Most pathogens cannot invade host cells once they are part of an antigen-antibody complex
Mostly done through antibodies acting alone
Act as agglutinins causing pathogens carrying antigen- antibody complexes to clump together, helps prevent them spreading through body and makes it easier for phagocytes to engulf multiple pathogens at the same time
Done by antibodies acting in complex
Act as antitoxins by binding to toxins produced and making them harmless
What is cell-mediated immunity
Where T-lymphocytes respond to the cells of an organisms that have been changed
E.g. by a virus, antigen processing, mutation or cells from transplanted tissue
Process of cell mediated immunity
- In the non-specific defence system, macrophages engulf and digest pathogens in phagocytosis
Process the antigens from the surface of pathogen and form antigen presenting cells (APCs) - Receptors on some T helper cells fit the antigens (clonal selection)
These T helper cells are activated to produce interleukins
These stimulate more T cells to divide rapidly by mitosis (clonal expansion)
Form clones of identical T helper cells that all carry the antigen to bind to a specific pathogen - The cloned T cells can:
Develop into T memory cells to respond rapidly on second infection
Produce interleukins that stimulate phagocytosis
Produce interleukins that stimulate B cells to divide
Stimulate development of a clone of T killer cells that are specific for the presented antigen and then destroy infected cells
What happens in humoral immunity
The body responds to antigens found outside the cells
E.g. bacteria, fungi and APCs
Humoral immune system produces antibodies that are soluble in the blood and tissue fluid and not attached to cells
How do antibodies and pathogen antigens interact in humoral immunity
B lymphocytes have antibodies on their cell surface membrane (immunoglobulin M)
Pathogens entering the body carry specific antigens or produce toxins that act as antigens
B cells with the complimentary antibodies will bind to the antigens on the pathogen or to free antigens
The B cells engulfs and processes the antigens to become an APC
Process of humoral immunity
Activated T helper cells bind to B cell APC
This is clonal selection: the point when the B cell with the correct antibody to overcome a particular antigen is selected for cloning
Interleukins produced by the activated T helper cells activate the B cells
Activated B cell divides by mitosis to give clones of plasma cells and B memory cells
This is clonal expansion
Cloned plasma cells produce antibodies that fit antigens on pathogen surface
They bind to and disable antigens or act as opsonins and agglutanins
This is primary immune response
Some cloned B cells develop into B memory cells
If body is infected by the same pathogen again, B memory cells divide rapidly to form plasma cell clones which produce right antibody to kill pathogen quickly
This is secondary immune response
Why do we get ill during an infection
Primary immune response takes days or weeks to become fully effective against pathogen
Symptoms are a results of the body reacting when pathogens are dividing freely, before the primary immune response is fully operational
What are autoimmune diseases
When the immune system stops recognising self cells and attack healthy body tissue
Can be caused by genetics, immune system responding abnormally to mild pathogen or normal bodily microorganisms or T regulator cells do not work effectively
Examples of autoimmune diseases
Rheumatoid arthritis
Lupus
What is rheumatoid arthritis
Immune system attacks cells in joints
Affects joints such as hands, wrists, ankles, feet
No cure
Treatment includes: immunosuppressants, pain relief
What is lupus
Affect skin and joints causing fatigue
Immune system attacks cells in connective tissue
Can attack any organ in the body such as liver, lungs or brain
No cure
Treatments include: immunosuppressants, steroids
How do plants respond to pathogen infection externally
An area of a plant that is under attack can warn separate areas of the infection via hormones, electrical signals or airborne compounds
When the areas detect these signals, they increase production of defensive compounds
This can also alert separate neighbouring plants of the infection as well
Plants under attack from insects can release chemicals into the air
This attract other insects (e.g. wasps) that can deter the attacking insects
What are antigens
Molecules that can stimulate an immune response
Our own antigens are recognised as ‘self’, foreign antigens stimulate the production of antibodies
Specific to the organism
Simple structure of antigens
Usually protein or glycoproteins with specific structure
On or inside the cell surface membrane
When does natural active immunity occur
Body produces T and B memory cells after being infected with pathogen
If you meet a pathogen for a second time, your immune system recognises the antigens more quickly and launches a secondary immune response before the pathogen causes disease
When does active artificial immunity occur
Active artificial immunity occurs when you become immune after you’ve been given a vaccination containing a harmless dose of antigen
When does artificial passive immunity occur
Artificial passive immunity is when you become immune after being injected with antibodies from someone else
E.g. being given antibodies to beat a disease via blood donation
What is passive immunity
Passive immunity is when you are given antibodies made by a different organism - your immune system doesn’t produce any antibodies of its own
When does natural passive immunity occur
Natural passive immunity is when a baby becomes immune due to the antibodies it receives from its mother, through the placenta and in breast milk
This lasts until the immune system of the baby begins to make its own antibodies
The antibodies received are likely to be relevant to pathogens in its environment
What is active immunity
Natural Active immunity results from having actually been infected by a pathogen.
This activates the immune system, leading to antibodies being formed by B cells.
Active immunity summary
Requires exposure to antigen
Takes a while for protection to develop
Protection is long term
Memory cells are produced
Passive immunity summary
No exposure to antigens
Protection is immediate
Protection is short term
Memory cells aren’t produced
What could a vaccine contain
Killed or inactivated bacteria and viruses
Attenuated (weakened) strains of live bacteria or viruses
Toxin molecules that have been altered and detoxified
Isolated antigens extracted from the pathogen
Genetically engineered antigens
Process of vaccination
Pathogen is made harmless so that the antigens are intact but there is no risk of infection
Small amounts of the safe antigen, known as the vaccine, are injected into the blood
The primary immune response is triggered by the foreign antigens and your body produces antibodies and memory cells as if you were infected with a live pathogen
If you come into contact with a live pathogen, the secondary immune response is triggered and you destroy the pathogen rapidly before you suffer symptoms of the disease
What is an epidemic
When a communicable disease spreads rapidly to a lot of people at a local or national level
What is an pandemic
When a disease spreads rapidly across a number of countries and continents
Why is mass vaccination usually most effective at the start of an epidemic
This prevents the spread of the pathogen into the wider population
When vaccines are being deployed to prevent epidemics, they often have to be changed regularly to remain effective
What is herd immunity
This is when a significant number of people in the population have been vaccinated
This gives protection to those who do not have immunity
There is minimal opportunity for an outbreak to occur
Why are booster vaccines given later
These make sure that memory cells are produced
These can be given several years after first vaccination
How is vaccination different from immunisation
Vaccination is the administration of a substance designed to stimulate the immune system
Immunisation is the process by why you develop immunity
Vaccination causes immunity
What are some routine vaccines offered to everyone
MMR:
Protects against measles, mumps and rubella and is given to children as an injection at around a year old and again before they start school
Contains attenuated measles, mumps and rubella viruses
Meningitis C vaccine:
Protects against bacteria that cause meningitis C
First given as an injection at 3 months and boosters are given to 1 year olds and teenagers
Why can vaccines change with the influenza vaccine for example
The flu vaccine changes every year
This is because antigens on the surface of the influenza virus change regularly to form new strains of the virus
Memory cells produced from vaccination with one strain of the flu will not recognise other strains with different antigens (strains are immunologically distinct)
Every year there are different trains of the influenza virus circulating in the population
This means a different vaccine must be made
Why may vaccine programmes change along with the vaccine (e.g. influenza vaccine)
Laboratories collect samples of these different strains
Organisations, such as the WHO (world health organisation) and CDC (centre for disease control), test the effectiveness of different influenza vaccines against them
New vaccines are developed and one is chosen every year that is most effective against the recently circulating influenza viruses
Governments and health authorities then implement a programme of vaccination using the most suitable vaccine
Why may someone be vaccinated when they are travelling
Sometimes people are given a vaccine that protects them from a strain causing an epidemic in another country
This helps stop the strain spreading globally
What is antigenic shift
The process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains
What is antigenic drift
A gradual process of genetic change that leads to more variety for each type of influenza virus due to there being different types of antigens on the surface
What happens in the primary response
When a pathogen enters the body for the first time, the antigens on its surface activate the immune system as the primary response
This response is slow because there aren’t many B lymphocytes that can make the antibody needed to bind to it
Eventually the body will produce enough of the right antibody to overcome the infection, this means that the person will show symptoms
T and B lymphocytes produce memory cells, which remains in the body for a long time and can remember the specific antigen and will recognise it the second time.
This means that the person is now immune
Why is the secondary response faster
If the same pathogen enters the body, the immune system will produce a quicker, stronger immune response (secondary response)
Clonal selection happens faster as memory B lymphocytes are activated and divide into plasma cells that produce the right antibody to the antigen
Memory T lymphocytes are activated and divided into the correct type of T lymphocytes to kill the cell carrying the antigen
This gets rid of the pathogen before you begin to show any symptoms
Summarised primary response
Pathogen enters first time
Slow response
B and T lymphocytes activated
Show symptoms
Summarised secondary responses
Pathogen enters for 2nd time
Response is fast
Memory cells activated
No symptoms
How are many medicinal drugs manufactured
Many are manufactured using natural compounds found in plants, animals or microorganisms
E.g. penicillin is obtained from penicillium fungus, cancer drugs can be made using soil bacteria, daffodils are now grown to produce a drug used to treat Alzheimer’s disease
Organisms that have already been studied could still prove to be useful sources of medicines as new techniques are developed for identifying, purifying and testing compounds
Why is maintaining biodiversity important for drug development
Species could die out before we get a chance to study them and we may never create cures for diseases such as AIDS
What are pharmocogenetics
This is a combination of drugs that work with your individual combination of DNA
Doctors can analyse your genetics and only prescribe drugs which will be most effective for you
This can mean that more effective drugs can be manufactured in the future using this information
How do genetics impact medication
Your genes determine how your body responds to certain drugs and different people respond to the same drug in different ways
This determines whether a drug is more effective or not
What is synthetic biology
This involves using technology to design and make things like artificial proteins, cells and even microorganisms
This can be applied to medicine where scientists can engineer bacteria to destroy cancer cells, while leaving healthy body cells intact by producing drugs which would otherwise be too rare, expensive or unavailable
How is nanotechnology involved in synthetic biology
This can also use nanotechnology where tiny, non natural particles are used for biological purposes e.g. to deliver drugs to specific sites within cells of pathogens or tumours
Stages of drug development
Phase 1: small number of healthy volunteers (establish how drug works and likely dose required
Phase 2: small number of patients (can be controlled, double blind or randomised experiments)
Phase 3: larger study of patients (assess and compare drug to existing treatments)
Licensing: if drug appears to have high efficacy, is safe, and meets manufacturing standards then it can be sold by licence holder in regions covered by regulatory authority
What are antibiotics
Chemicals which kill or inhibit the growth of bacteria
Used by humans as drugs to treat bacterial infections
They target bacteria cells without damaging body cells
Why have the deaths from bacterial infections dropped recently
We have been able to beat bacterial infections easily using antibiotics so the death rate has fallen
This have been happening since the discovery of penicillin (from penicillium mould) by Alexander Fleming and the chemical’s use during the Second World War
Possible risks from using antibiotics
Can develop severe allergic reactions in some people
Antibiotic resistance
How do bacteria become resistant to antibiotics
There is genetic variation in a population of bacteria
Genetic mutations make some bacteria naturally resistant to an antibiotic
The ability to resist an antibiotic is an advantage over competition as the bacteria are able to survive in a more hostile environment (due to antibiotics providing selection pressure) so they live longer and reproduce by binary fission
Resistance alleles are also passed laterally through the population by conjugation in the form of plasmids
The allele for antibiotic resistance is passed on to lots of offspring
So resistance spreads and becomes more common in a population of bacteria over time
Why is antibiotic resistance a problem for patients of bacterial infections
If the bacteria has developed resistance then the infection cannot be treated as easily using antibiotics so the infection can become more severe which could lead to death
What can be a product of antibiotic resistance
Can lead to the development of superbugs that are resistant to most known antibiotics
These are becoming more common
We are less able to treat some potentially life threatening bacterial infections
What is MRSA
Stands for Meticillin resistant staphylococcus aureus
This causes serious wound infections such as septicaemia
It is resistant to several antibiotics (including meticillin)
Carried by up to 30% of population on skin or in nose
What is C. difficile
Clostridium difficile
Infects the digestive system which causes problems in people who have already been treated with antibiotics
Could be caused by harmless bacteria that are present in the digestive system which are killed by the antibiotics, which C. difficile is resistant to
Causes C.difficile to flourish due to lack of competition
It produces a toxin causing severe diarrhoea, fever or cramps
How to help prevent bacterial antibiotic resistance
Doctors should not prescribe antibiotics for minor infections
Should not prescribe them to prevent future infections (except patients with weak immune systems, e.g, elderly people or HIV patients)
Patients should take all the antibiotics they’re prescribed to fully clear the infection and all bacteria are killed
B lymphocyte diagram
Phagocytes diagram
Primary and secondary response graph
Primary response starts around the 5th - 10th day
Secondary starts around 25-28 days
What type of molecule is callose
Polysaccharide
T lymphocyte diagram
