12 - Communicable Diseases Flashcards
What parts of the plant does Ring Rot damage?
Leaves, tubers and fruit
What causes a communicable disease?
A pathogen
What are the 4 main types of pathogen?
- Bacteria 2. Viruses 3. Protoctista 4. Fungi
What does a vector do?
Carry pathogens from one organism to the other
How are communicable diseases in plants spread?
Directly plant-to-plant
What proportion of bacteria cause communicable disease?
Only a small proportion
What are the two main ways bacteria are classified?
- By shape 2. By cell wall
What shape are bacilli?
Rod-shaped
What is chain of bacilli bacteria called?
Strepto-species type i.e. Streptobacilli
What is a cluster of cocci bacteria called?
Staphylo-species type i.e. staphylococci
What shape is a vibrios?
Comma shaped
What is a corkscrew-shaped bacterium called?
Spirochaetes
What shape is a coccus?
Spherical
What are the two types of bacterial cell wall?
Gram-positive and gram-negative
What colour do gram-positive bacteria go with gram staining?
Purple-blue
What colour do gram-negative bacteria go with gram staining?
Red
What are some features of a gram-positive cell wall (excluding colour with gram staining)
Thicker but less tough, more susceptible to antibiotics which damage the cell wall, more peptidoglycan, lower lipid content, more prominent mesosome
What makes a gram-positive cell wall go purple-blue with gram staining?
The peptidoglycan in their cell wall retains crystal violet stain
What are some features of a gram-negitive cell wall (excluding colour with gram staining)?
Thinner but tougher, higher lipid content due to outer cell membrane, less susceptible to antibiotics
What is an example of a bacterium with a gram-positive cell wall?
MRSA
What is an example of a bacterium with a gram-negative cell wall?
E.coli
What is a bacterial cell wall mostly made up of?
Peptidoglycan
What is the structure of peptidoglycan?
Massive disaccharide polymers cross-linked by short chains of identical amino acid monomers
What is the basic structure of any virus?
Some genetic material (either DNA or RNA) surrounded by a protective protein coat
What is the mechanism of infection of a virus?
They attach to the cell and inject their genetic material, which takes over the biochemistry of the host cell to make more viruses by inserting itself into the host DNA, until so many are made that the host cell is lysed (bursts) and the new viruses are released
What 2 things make viruses very successful pathogens?
They reproduce rapidly and evolve by developing adaptations to their host
What proportion of naturally occurring viruses are pathogenic?
All of them
How many other types of organism do viruses infect?
Every other type of organism, including other viruses
What is a bacteriophage?
A virus which attacks a bacteria
What is a virophage? Give an example
A virus which infects other viruses, such as the Sputnik virus
Are protoctista eukaryotic or prokaryotic?
Eukaryotic, with a wide variety of feeding methods
What proportion of protoctista are pathogenic?
Only a small percentage, most are harmless
What are fungi a major problem for?
Some plants- they tend not to be a major problem for animals
Are fungi eukaryotic or prokaryotic?
Eukaryotic
Are protoctista unicellular or multicellular?
Unicellular, although they can group into colonies
Are fungi unicellular or multicellular?
Usually multicellular, with the exception of yeasts
How do fungi feed?
Many are saprophytes, but the pathogenic ones are parasites and eat living organisms. They can’t photosynthesise, so digest food outside of their cells before absorbing the nutrients
What do saprophytes feed on?
Dead and decaying matter
What part of a plant do many plant fungal diseases affect?
The leaves, stopping the plant photosynthesising and killing it rapidly
How do fungi reproduce?
They produce millions of spores, which can spread huge distances and spread their disease quickly among crops
What organelles does yeast have?
Nucleus, mitochondria, cell membrane and a permanent vacuole
Apart from yeast organelles, what organelles may a more complex fungus have?
A cell wall (and vesicles) and food storage granules of starch
What are the two main pathogenic modes of action?
- Damaging host tissue directly 2. Producing toxins which damage host tissue
What is the mechanism of infection of fungi?
They digest and destroy living cells. This, combined with the response of the body to the damage caused by the fungus, causes the disease
What is the mechanism of action of protoctista which damage host tissue directly?
They take over cells and lyse them as a new generation emerge, but do not take over the genetic material of the cell like a virus; instead, they digest and use the cell contents as they reproduce
Apart from bacteria, what type of pathogen can produce cytotoxins?
Fungi
Are bacterial toxins produced deliberately to damage the host?
No, they are a by-product of the natural function of the bacterial cell
What is the mechanism of action of most pathogenic bacteria?
They produce toxins which poison/damage the host cells in some way
What are 3 ways bacterial toxins can damage cells?
- Breaking down cell membranes 2. Damaging/deactivating enzymes 3. Interfering with the host DNA so the cell can’t replicate
What organisms does tuberculosis affect?
Humans, cows, pigs, badgers and deer
What type of pathogen is tuberculosis caused by?
Bacteria
People suffering from what other disease are more likely to suffer from tuberculosis?
HIV/AIDS
How is TB cured and prevented?
Cured with antibiotics, prevented by vaccination or better living standards
How is TB spread in humans?
Droplet infection
What is the mechanism of TB?
It damages and destroys lung tissue and suppresses the immune system so that the body is less able to fight off other diseases
How is bacterial meningitis spread?
By droplet infection
How is bacterial meningitis cured and prevented?
Curable with antibiotics if administered early enough, vaccines can protect against some forms
What are the mechanism and symptoms of bacterial meningitis?
Infection of the meninges (protective membranes on brain surface) which can spread to the rest of the body and cause fatal septicaemia. Symptoms vary depending on type of bacteria, but all share a blotchy red/purple non-blanching rash
Who are the main groups affected by bacterial meningitis?
Very young babies and 15-19 year olds
What is the mechanism of the HIV virus?
It attacks T helper cells, which gradually destroys the immune system and leaves sufferers vulnerable to secondary infection
What type of virus is HIV/AIDS?
A retrovirus
How does a retrovirus work?
A virus that is composed not of DNA but of RNA. Retroviruses have an enzyme, called reverse transcriptase, that gives them the unique property of transcribing their RNA into DNA after entering a cell. The retroviral DNA can then integrate into the chromosomal DNA of the host cell, to be expressed there.
What animals does bacterial meningitis affect?
Humans
What animals does HIV/AIDS affect?
Humans and some other primates
How is HIV spread?
Passed between people via infected bodily fluids i.e. via unprotected sex, shared needles, contaminated blood and mother to baby through either pregnancy or breastfeeding. FGM also increases its spread if equipment is reused
How is HIV cured?
No vaccine or cure but antiretroviral drugs can slow its progress
What animals does influenza affect?
Mammals and birds
What is the mechanism of influenza?
Infects ciliated epithelial cells in the gas exchange system, killing them and leaving the airways vulnerable to secondary infections such as bacterial pneumonia
What are the 3 types of influenza and which is most virulent?
A,B,C, with A being most virulent
Why is a vaccine made each year for flu?
Because flu viruses undergo small, regular mutations, so their surface antigens are constantly being reshuffled
Is the a cure for flu?
No
What is zoonosis and give an example of something that does it?
Where a disease can spread from animals to humans. An example would be influenza (swine flu or bird flu)
What causes malaria?
Several species of protoctista from the genus Plasmodium, with the most common being Plasmodium Falciparum, spread by the bite of the female Anopheles mosquito
What is the mechanism of malaria?
Infects red blood cells, liver, brain. Disease recurs, making people weak and vulnerable to secondary infection
What is the cure for malaria?
No vaccine and limited cures such as quinine, but preventative measures such as vector control through mosquito nets etc. can be very effective
What are 2 reasons malaria can be difficult to treat?
- Protoctista ‘hides’ inside red blood cells 2. Caused by several different species so surface antigens may be different
What causes ringworm?
Fungi, with different fungi affecting different species.
What is a cure for ringworm or Athlete’s Foot?
Antifungal creams
What are the symptoms of ringworm?
Grey-white, crusty, infectious circular area of skin which aren’t damaging but are unsightly and itchy
What causes Athlete’s Foot?
Tinia Pedia, a form of human ringworm fungus
Where does the Athlete’s Foot fungus typically grow?
The warm, moist skin between toes, which it digests
What are the symptoms of Athlete’s Foot?
Cracking and scaling which is itchy and may become sore
What animals does ringworm affect?
Mammals
What plants does Ring Rot affect?
Potatoes, tomatoes and egg plant
What is the cure for Ring Rot?
There is none
What happens to a field once it has been infected by Ring Rot?
It cannot be used to grow potatoes, tomatoes or egg plants for at least 2 years
What type of pathogen causes Ring Rot?
A bacterium
What does TMV infect?
Tobacco plants and 150 other species
How is TMV prevented and cured?
Resistant crop strains can prevent it but there is no cure
What is the mechanism of TMV?
Damages leaves, flowers and fruit, stunting growth and reducing yield, and can leads to almost total crop loss
What is Potato late blight caused by?
A fungus-like protoctista called an oomycete
How is Potato late blight prevented and cured?
No cure but can be prevented via use of resistant strains, careful management and chemical treatments
What is the mechanism of Potato late blight?
Hyphae penetrate host cells and destroy leaves, tubers and fruit, leading to millions of pounds of crop damage per year
What type of pathogen causes Black Sigatoka?
A fungus
What type of plant does Black Sigatoka affect?
Bananas
What part of the plant does Black Sigatoka affect?
The leaves
What is the mechanism of Black Sigatoka?
Hyphae penetrate and digest cells, turning leaves black. Can cause 50% reduction in yield of infected plants
How is Black Sigatoka cured and prevented?
No cure but resistant strains being developed and good husbandry and fungicide treatment can control the spread of the disease
What are the two main types of transmission of communicable diseases between animals?
Direct and indirect
What are the three main types of direct transmission in animals?
- Inoculation 2. Direct contact 3. Ingestion
What happens in ingestion in the direct transmission of animal pathogens?
Contaminated food of drink are ingested or pathogens are transferred from the hands to the mouth
What are two examples of diseases spread by ingestion?
- Amoebic dysentery 2. Diarrhoeal diseases
What are 3 ways pathogens can be spread via inoculation?
- Animal bite i.e. rabies 2. Break in the skin i.e. unprotected sex 3. Puncture wound or shared needles i.e. septicaemia
What are 3 ways pathogens can be spread via direct contact?
- Direct skin-to-skin contact i.e. ringworm, athlete’s foot 2. Kissing or any contact with another person’s bodily fluids i.e. many STDs or bacterial meningitis 3. Microorganisms from the faeces transmitted on the hands i.e. many diarrhoeal diseases
What are the 3 main types of indirect transmission of pathogens between animals?
- Formites 2. Vectors 3. Droplet infection
What is a formite infection?
Where an inanimate object such as socks, bedding or cosmetics can transfer pathogens
What are 3 types of pathogen spread by formite infection?
- Gas gangrene 2. Athlete’s foot 3. Staphylococcus infections
What occurs during a droplet infection?
Minute droplets of saliva or mucus are expelled from the mouth during talking, coughing or sneezing; if the droplets contain pathogens, anyone who inhales them may contract the illness
What are two types of disease which can be spread by droplet infection?
TB or influenza
What are the most common types of vector to spread diseases between animals?
Animals such as malaria-carrying mosquitoes, dogs, foxes and bats carrying rabies, fleas carrying the plague
What is a non-animal example of a vector (to spread diseases between animals)?
Water, which can transmit diarrhoeal diseases
What disease can be transmitted between sheep and humans?
Brucellosis
How can the risk of zoonotic infection be reduced?
Washing hands after any contact with animals
What are some factors which can increase the risk of transmission of diseases between animals? (7)
- Poor nutrition 2. Overcrowded working and living conditions 3. A compromised immune system 4. Climate change, which can introduce new vectors and diseases to areas 5. In humans, poor disposal of waste provide a breeding grounds for vectors 6. Culture and infrastructure- in many countries, traditional practices can increase transmission 7. Socioeconomic factors such as a lack of trained health workers and insufficient public warning of outbreaks
Can plant pathogens be transmitted directly?
Yes, if a part of a healthy plant comes into direct contact with a part of an infected plant
What are some plant pathogens which can be transmitted directly?
Ring rot, TMV, black sigatoka, potato late blight
What are the two main types of indirect transmission of pathogens in plants?
- Soil contamination 2. Vectors
How are plant pathogens transmitted via soil contamination?
Infected plants often leave pathogens or spores from fungi/protoctista in the soil, which can infect the next crop. Some pathogens or their spores can also survive the composting process, so the contaminated compost can infect plants it is spread on
What are the 4 main types of vectors which spread plant pathogens?
- Wind 2. Water- spores swim in the film of surface water on leaves, and both spores and pathogens can be carried by raindrops 3. Animals- Insects and birds can carry pathogens and spores, and aphids can inoculate directly 4. Humans- Hands, clothing, fomites, farming practices and the transport of crops
What are some factors affecting the spread of communicable diseases between plants?
- Planting varieties of crops which are susceptible to disease 2. Overcrowding increasing the likelihood of contact 3. Poor mineral nutrition reducing plants’ resistance 4. Damp, warm conditions increasing the survival and spread of pathogens and spore 5. Climate change- increased rainfall and wind, new animal vectors, although drier conditions may reduce spread of disease
What are 3 things which act as physical barriers to pathogens in plants?
- Waxy cuticle of leaves 2. Bark on trees 3. Cellulose cell wall
What is different about plants’ and animals’ responses to infection?
Animals attempt to heal damaged tissue, but plants just seal it off and sacrifice it
What are 3 cellular responses to infection in plants?
- Producing defensive chemicals 2. Physically strengthening cell walls 3. Sending alarm signals to unaffected cells to trigger their defences
What 2 things can receptors in plant cells respond to upon infection?
- Molecules from the pathogen 2. Chemicals produced when the plant cell wall is attacked by pathogenic enzymes
What is stimulated when receptors in a plant cell detect an infection?
The release of signalling molecules, which appear to switch on genes in the nucleus, in turn causing the 3 cellular responses to infection
What two polysaccharides are made to strengthen plant cell walls upon infection?
Callose and lignin
What is the structure of callose?
Polysaccharide made up of beta glucose with 1-3 and 1-6 carbon linkages
What does callose do when a plant cell is infected?
- Block sieve plates in the phloem, sealing off the infected part 2. Is deposited in the plasmodesmata between healthy cells and their neighbours 3. Within minutes of attack, synthesised and deposited between cell membrane and cell wall of cells neighbouring infected one. 4. More callose and lignin then added, strengthening the wall even further
What are some examples of plant chemical defences against pathogens? (6)
- Insect repellants 2. Anti-fungals 3. Insecticides 4. Antibacterial compounds (including antibiotics) 5. Anti-oomycetes 6. General toxins
What is an example of a general toxin made by plant cells as a chemical defence against pathogens?
Chemicals which can be broken down to make cyanide compounds
What are some examples of insect repellents made by plants?
Citronella from lemon grass or pine resin
What are some examples of insecticides made by plants?
Caffeine or pyrethrins, which are made by chrysanthemums and is an insect neurotoxin
What are some example of some antibacterial compounds made by plant cells?
- Phenols 2. Gossypol 3. Defensins, plant proteins which disrupt bacterial and fungal cell membranes
What is gossypol?
A chemical made by cotton which has antibacterial and antifungal properties
What are phenols used for in plants?
As an antiseptic and antifungal agent
What are some examples of antifungal chemicals made by plants?
- Phenols 2. Gossypol 3. Caffeine 4. Saponins- chemicals found in many plant cell membranes which interfere with fungal cell membranes 5. Chitinases- enzymes to break down chitin in fungal cell walls
What is caffeine toxic to?
Insects and fungi
What is an example of an anti-oomycete made by plants?
Glucanases, which are enzymes which can break down glucans, polymers found in the cell walls of many oomycetes
What are the two mammalian lines of defence against pathogens?
- Primary non-specific defences 2. Specific immune response
What is the outermost layer of the skin called?
The epidermis
What does the skin produce to inhibit pathogenic growth?
Oily sebum
What are the 3 ways skin serves as a defence against pathogens?
- Oily sebum 2. Physical barrier 3. Skin flora of microorganisms
How does the flora of healthy microorganisms on the skin help it serve as a barrier to pathogens?
These out-compete pathogens for nutrients and space
What is the structure of the part of the skin which serves as a barrier to pathogens and how is it produced?
The epidermis has several layers, mostly made of cells called keratinocytes. As these move through the epidermis they dry out and the cytoplasm is replaced by keratin, with this layer acting as a barrier.
What are some examples of primary non-specific defences against disease in mammals which aim to keep pathogens out? (7)
- Skin 2. Mucous membranes 3. Digestive system 4. Tears 5. Urine 6. Expulsive reflexes 7. Blood clotting
What are some examples of primary non-specific defences against disease in mammals which work to get rid of pathogens?
- Inflammation 2. Fever 3. Phagocytes
What are some examples of places that mucous membranes involved in the defence of the body against pathogens are found?
Airways, reproductive system, lungs, digestive system, gut, genitals, anus, ears and nose.
What are the two main types of cell which mucous membranes contain?
Goblet cells and ciliated epithelial cells
How do goblet cells help keep out pathogens?
They secrete sticky mucus, which traps pathogens and contains phagocytes and also lysosomes, which contain enzymes called lysozymes which can kill bacteria and fungi by destroying their cell walls
How do ciliated epithelial cells help keep out pathogens?
They waft mucus containing pathogens to places where it can be destroyed or expelled; for example, in the airways they waft it to the top of the trachea, where it can move into the oesophagus for expulsion
How does stomach acid act as a barrier to pathogens?
It is very acidic at pH 1-2, so can denature pathogens’ enzymes
How do tears and urine act as a barrier to pathogens?
They both contain lysosomes, and tears have ions to lower their water potential and potentially crenate pathogens
What are 4 examples of expulsive reflexes and what do they all do?
Coughing, sneezing, vomiting and diarrhoea all eject pathogen-laden fluids from the body
What are the two most important chemicals released by platelets in a blood clot and what do they do?
- Serotonin- Makes smooth muscle in blood vessel walls contract, reducing bloodflow 2. Thromboplastin- Triggers the blood clot cascade of reactions
What do platelets attach to in a blood clot?
The skin or damaged cells which release substances that attract platelets
What happens in wound repair after a blood clot has formed?
- Cut dries to form a scab 2. Epidermal cells below scab reproduce to seal off wound permanently 3. Damaged blood vessels regrow 4. Collagen fibres deposited to give new tissue strength 5. Once new epidermis reaches normal thickness, scab sloughs off
What chemicals cause a fever?
Cytokines, which stimulate the hypothalamus to ‘reset’ the body thermometer to a higher temperature
How does fever work to get rid of pathogens?
Pathogens can’t reproduce as well at a higher temperature and the specific immune response works faster at a higher temperature
What is inflammation characterised by?
Redness, swelling, pain, heat and possibly a full body rash if the infection is widespread
What two chemicals are released by activated mast cells in damaged tissue?
Histamines and cytokines
What do cytokines do in inflammation?
Attract white blood cells to the site of the wound to dispose of pathogens by phagocytosis
What is oedema?
Swelling caused by a large accumulation of tissue fluid
What do histamines do in inflammation?
Cause smooth muscle in the walls of blood vessels to relax, which: 1. Causes the blood vessel to dilate, raising local temperature to disadvantage pathogens and causing heat and redness 2. Makes the blood vessel walls more leaky, causing oedema and pain
What are the two main types of phagocyte?
Neutrophils and Macrophages
Where are neutrophils and macrophages made?
Bone marrow
What type of nucleus does a neutrophil have?
Multi-lobed
Where are neutrophils found?
Blood, tissue fluid and epithelial surfaces
Are neutrophils long or short-lived?
Short-lived
What is pus made up of?
Dead phagocytes and pathogens
Are macrophages smaller or larger than neutrophils?
Larger
What do macrophages travel in the blood as?
Monocytes
Where do macrophages develop and settle?
The lymph nodes
How long does is usually take a human neutrophil to engulf and destroy a bacterium?
Under 10 minutes
What is a phagosome-lysosome complex called?
Phagolysosome
Why do macrophages take longer than neutrophils to digest a pathogen?
They produce a MHC from a pathogenic antigen and become an antigen-presenting cell
What is an APC?
An antigen-presenting cell, which is a macrophage with at least one MHC
What are the stages of phagocytosis?
- Phagocyte attracted to pathogen by chemicals the pathogen produces 2. Phagocytes recognise non-human proteins on the pathogen, and a glycoprotein on the cell-surface membrane of the phagocyte binds to a pathogenic antigen 3. Pathogen is engulfed into a vesicle called a phagosome 4. Phagosome combines with lysosome to form phagolysosome, with enzymes destroying the pathogen 5. If the cell is a macrophage, pathogenic antigens can be combined with proteins to form an MHC, which is presented on the cell surface to stimulate other immune cells
What chemicals do phagocytes containing a pathogen produce?
Cytokines
What do opsonins do?
They ‘tag’ pathogens to make them more easily recognisable by phagocytes, which have opsonin-binding sites on their cell surface membrane
What are two examples of opsonins?
Immunoglobulin G and Immunoglobulin M
What type of biological molecule is an antibody?
Polypeptide/protein
What are 3 places a T or B lymphocyte can come across an antigen?
- A pathogen in bodily fluids 2. MHC on a macrophage 3. Infected cell
Where are T lymphocytes activated?
Thymus
Where are B and T lymphocytes produced?
Bone marrow
How long does the specific immune response take to respond to a new pathogen?
Up to 14 days
What are the two chain types in an antibody?
Heavy chain and Light chain
What is the part of an antibody which is the same across all antibodies called?
Constant region
What is the part of an antibody which changes from antibody to antibody called?
Variable region
What are the polypeptide chains in an antibody joined by?
Disulfide bridges
How many polypeptide chains make up an antibody?
4 (2 heavy, 2 light)
Which parts of an antibody form antigen-binding sites?
The variable regions
What is the purpose of the hinge region of an antibody?
Allows flexibility when the antibody binds to the antigen
What is the purpose of the constant region of an antibody?
Allows binding to receptors on immune system cells such as phagocytes
What are the 3 ways antibodies can help clear an infection?
- Agglutinating Pathogens 2. Neutralising toxins 3. Preventing the pathogen binding to human cells
How many antigens can an antibody bind to at once?
2
Why are antigen-antibody complexes easily engulfed and digested by phagocytes?
The antibodies act as opsonins
How do antibodies neutralise toxins?
They are bound to any other antigen, and the antibody-toxin complex is phagocytosed
How does the agglutination of pathogens by antibodies help clear the body of infection?
Because antibodies have two binding sites, they can bind to antigens on two different pathogens at once, causing them to clump together and allowing lots of pathogens to be phagocytosed at once
What are antibodies which agglutinate pathogens called?
Agglutinins
How do antibodies prevent pathogens binding to human cells?
When binding to antigens on the pathogen, they can block the cell surface receptors which pathogens require to bind to host cells, so the cells cannot be attached to or infected
Where do B lymphocytes mature?
The bone marrow
What are the 4 main types of T lymphocytes?
- T regulator 2. T helper 3. T killer 4. T memory
Which 2 harmful chemicals do T killer cells use?
Hydrogen peroxide and perforin
How does perforin kill pathogens?
It makes holes in their cell surface membrane so that it is freely permeable
What do T lymphocytes respond to in cell-mediated immunity?
A cell of the organism which has been changed in some way, such as a cell infected virally, one presenting antigens or one which has undergone a random genetic mutation, or cells from transplanted tissue
What is the purpose of a T killer cell?
Kill pathogens using harmful chemicals
What are the 3 types of B lymphocyte?
- Plasma cell 2. B effector cell 3. B memory cell
What is the purpose of a B effector cell?
Differentiate into the required plasma cell
What is the purpose of a plasma cell?
Produce antibodies specific to the pathogen
How many antibodies can a plasma cell produce when active?
~2000 antibodies per second
What is the lifespan of a plasma cell?
A few days
What is the purpose of a B memory cell?
Live a very long time an remember a particular antigen so that the body can mount a quick response to it if necessary
What is the purpose of a T memory cell?
Live a very long time and remember a pathogen, then produce lots of T killer cell clones if it is ever encountered again
What chemicals are important in the function of T regulator cell?
Interleukins
What is the purpose of a T regulator cell?
Stop the immune system once an infection is over, prevent the body setting up an autoimmune response and ensuring that it recognises self antigens
What type of receptor on the surfaces of T helper cells bind to MHCs on APCs?
CD4
What are interleukins a type of?
Cytokine
What do T helper cells produce?
Interleukins
What do the interleukins produced by T helper cells do?
Stimulate the activity of B cells, which in turn stimulates the production of antibodies, stimulates production of other types of T cell by mitosis, and attracts and stimulates macrophages to ingest pathogens with antibody-antigen complexes
What is cell mediated immunity especially important against?
Viruses and early cancers
What type of cell can T helper cells differentiate into?
T memory cells
How long does it take for antibodies to start to be produced after an infection?
Around 5 days
What happens in clonal selection?
The undifferentiated T or B lymphocyte has a receptor complementary to the pathogen’s antigen (either in an MHC in cell mediated immunity or on a pathogen in humoral immunity). It binds to the antigen using this, and the lymphocyte then divides rapidly by mitosis
What does the body respond to in humoral immunity?
Antigens found outside of cells (for example on pathogens) or on APCs
What is clonal expansion?
Where a B cell activated by interleukins divide to give clones of plasma cells and B memory cells
What is the primary immune response?
The response to a previously unseen pathogen, where it can take days or weeks for the correct antibody to be produced
What is the secondary immune response?
Where B and T memory cells respond rapidly to a known pathogen and quickly deal with the infection
What type of antibodies does humoral immunity produce?
Ones which are soluble in blood and tissue fluid, and not attached to cells
What are 3 examples of autoimmune diseases?
- Lupus 2. Type 1 diabetes 3. Rheumatoid arthritis
What part of the body does Type 1 diabetes affect?
Insulin-secreting cells of the pancreas
What are some symptoms of Type 1 diabetes?
Extreme thirst, weight loss, blurred vision, fatigue, weakness
What are some treatment methods for Type 1 diabetes?
Insulin injections, pancreas transplant, immunosuppressant drugs
Are Lupus or Rheumatoid arthritis curable?
No, you can only manage their symptoms
What parts of the body are affected by Rheumatoid arthritis?
The joints, especially those in the hands, wrists, ankles and feet
What are some symptoms of Rheumatoid arthritis?
Tender, swollen, warm joints, joint stiffness, fatigue, fever, weight loss
What are some treatment options for Rheumatoid arthritis?
Steroids, pain relief, immunosuppressants, anti-inflammatory drugs
What parts of the body are affected by lupus?
Often the skin and joints but can affect any organ in the body including the kidneys, liver, lungs and brain
What are some symptoms of Lupus?
Fatigue, aching joints, skin rash, fever, hair loss, seizures, sores on the mouth and/or nose
What are some treatment options for Lupus?
Steroids, anti-inflammatories, immunosuppressants, various other such as transplant of the infected organ
What is an autoimmune disease?
One in which the immune system stops recognising its own cells and starts attacking healthy tissue
What is a disadvantage of using immunosuppressant drugs to treat autoimmune disease?
This deprives the body of its natural defence against communicable disease
What causes autoimmune disease?
It is not fully understood by science but there is a genetic tendency in some families, sometimes T regulator cells don’t work properly and sometimes the body reacts badly to a normally mild pathogen
How many recognised types of autoimmune disease are there?
Around 80 which can cause chronic inflammation or the complete destruction or breakdown of healthy tissue
What are the 4 main types of immunity?
- Natural 2. Artificial 3. Passive 4. Active
What is active immunity?
Immunity provided by activation of the immune system
What are 5 examples of different antigenic material used in vaccines and diseases each would be used for?
- Whole, live microorganisms (smallpox) 2. A dead pathogen (cholera and typhoid) 3. A harmless or attenuated (reduced virulence) virus (Measles) 4. A preparation of antigens (Hepatitis B) 5. Some harmless toxin (tetanus)
What is passive immunity?
Provided by antibodies which have not been manufactured by stimulating the recipient’s immune system
What is natural immunity?
Achieved as the result of the entry of a pathogen and its antigenic material, which stimulates an immune response
What is artificial immunity?
Gained by deliberate exposure to antibodies or antigens
Give an example of natural passive immunity
Antibodies provided via the placenta or breast milk
Give an example of artificial passive immunity
Immunity provided by injection of antibodies made by another individual
Give an example of natural active immunity
Immunity provided by antibodies made in the immune system as a result of infection
Give an example of artificial active immunity
Immunity provided by antibodies made in the immune system as a result of a vaccine
How old do you have to be before your body starts making antibiodies?
At least a couple of months old
What is colostrum and why is it special?
The first milk a mammalian mother makes, special because it is very high in antibodies
What does the infant gut do to antibodies found in the colostrum?
Allows them to pass into the bloodstream without being absorbed
What is notable about the type of antibodies in colostrum?
They are likely to be relevant to pathogens found in the environment, where the mother encountered them
How long does natural passive immunity last? (Specifically in new borns)
Until the baby begins making its own antibodies
Where are the tetanus antibodies used in vaccines extracted from?
The blood of horses
How does vaccination work?
- Small amounts of safe antigen (the vaccine) are injected into the blood 2. The body’s primary immune response is triggered and it works as if the antigens were a real pathogen 3. If the pathogen ever does enter the body, memory cells left over from the first injection will cause the secondary immune response to rapidly kill all pathogens and prevent symptoms of an infection
What is an epidemic?
When a communicable disease spreads rapidly to a lot of people on a local or national level
What is a pandemic?
When a communicable disease spreads rapidly to a lot of people on an international or intercontinental level
When is ring vaccination used?
When a new case of a disease is reported
What is ring vaccination used for today apart from in treating human diseases?
To control the spread of livestock diseases
What is ring vaccination?
Where you vaccinate all people in the immediate vicinity of new cases of a disease, which could be in the surrounding houses, a whole village/town, or in a hospital ward
What is herd immunity?
Using a vaccine to provide immunity to all or almost all of a population at risk- once enough people are vaccinated (which varies depending on the disease), the disease can no longer spread
What are two examples of prevalent diseases which we so far do not have a vaccine for?
Malaria and HIV/AIDS
Why is Malaria so hard to make a vaccine for?
The plasmodium parasite spends a lot of time in erythrocytes so is protected from the immune system by self antigens, and once in the body the surface antigens of the parasite can reshuffle
Why is HIV/AIDS so hard to make a vaccine for?
It enters the macrophages and T helper cells, so disables the immune system itself
What are some examples of medicines which treat symptoms?
Anti-acid drugs for indigestion, anti-inflammatories, painkillers
What are some examples of medicines which cure diseases?
Chemotherapy drugs for some cancers, antibiotics, antifungals
What was the first widely used antibiotic and where is it derived from?
Penicillin, derived from a fungal mould
When was Penicillin first discovered and by whom?
1928 by Alexander Fleming
What are the two broad types of antibiotics?
Bactericidal and bacteriostatic antibiotics
What do bactericidal antibiotics do?
Kill bacteria, either by interfering with the cell wall or with the cell contents
What do bacteriostatic antibiotics do?
Stop bacteria from multiplying by interfering with either bacterial protein production or DNA replication
What medicine is extracted from foxgloves and what is it used to treat?
Digitoxin, a powerful heart drug used to treat atrial fibrillation and heart disease
Where is vancomycin extracted from and what is it used for?
Extracted from soil fungus, used as an antibiotic
What is prialt and where is it extracted from?
A painkiller 1000 times more powerful than morphine, extracted from a cone snail
What drug can be extracted from the bark of a willow tree and what is it used for?
Aspirin (in which the active ingredient is salicylic acid), used as a painkiller, anti-inflammatory, anti-coagulant and anti-pyretic (to reduce fever)
What two drugs can be extracted from a yew tree and what are they used for?
Docetaxel and paclitaxel, which are used to treat some forms of breast cancer
What is a negative effect of loss of biodiversity on medicine?
Many medicines are naturally derived, so we may be losing out on undiscovered medicines if undiscovered species are wiped out
What are some modern methods of discovering new medicines?
Using computers to build 3D models of pathogens, antigens and drugs for analysis, using computers to search through huge libraries of chemicals for useful ones, analysis of pathogenic or cancerous cell genomes
What is pharmacogenetics?
The science of interweaving knowledge of molecular drug actions with a knowledge of a person’s genetic material
What are some ways in which medicine will likely change in the future?
Increase in personalised medicine based on pharmacogenetics, use of synthetic biology to develop and produce new drugs, use of nanotechnology to deliver drugs more precisely
What does synthetic biology enable us to do?
Genetically engineer bacteria or even mammals to produce medicines cheaply, quickly and efficiently
What is selective toxicity in terms of antibiotics?
Where antibiotics interfere with bacterial metabolism without affecting the host cells
How do penicillin and cephalosporins work?
They damage the bacterial cell wall, causing the bacterium to be more easily damaged by the immune reaction
How do polymixines work?
They make holes in the bacterial cell membrane, affecting it’s permeability
How do tertracyclines and streptomycin work?
They inhibit bacterial protein synthesis
How do sulfonamides work?
They interfere with bacterial metabolic reactions
What are two notable examples of antibiotic-resistant bacteria?
MRSA and C.Difficile
What is MRSA?
Methicillin Resistant Staphylococcus Aureus, a bacterium carried by up to 30% of the population on the skin or in the nose, which causes boils, abscesses and potentially fatal septicaemia, and which is resistant to methicillin
What is C.Difficile?
Clostridium Difficile, a bacterium in the guts of around 5% of the population which produces toxins that damage the lining of the intestines, leading to diarrhoea, bleeding and sometimes death.
When does C.Difficile become a problem for someone?
When commonly used antibiotics kill off gut bacteria but it survives due to resistance, allowing it to reproduce and take hold rapidly
What was the first new antibiotic found in the last 30 years?
Teixobactin
What is the Longitude Award?
A £10 million reward for developing an accurate, cost-effective and easy-to-use test for bacterial infection
What are some long-term methods of reducing the number of antibiotic-resistant bacteria?
- Minimising the use of antibiotics 2. Making sure that courses of antibiotics are completed 3. Good hygiene in hospitals, care homes and in general
What are some ways in which the problem of antibiotic resistance is being combated?
New antibiotics are being searched for and developed, adding antibiotics to animal feed to prevent infection banned in the UK
What is the cascade of blood clot reactions?
Platelets arrive at the damaged tissue and release thromboplastin. This , Calcium ions and prothrombin catalyses into thrombin. Thrombin then catalyses fibrinogen into fibrin which then forms a clot.
What is a spiral shape bacteria called?
Spirillum
What are all the different types of bacteria
Bacilli (rod), chain of bacilli (streptobacilli), coccus (spherical), pair of cocci, chain of cocci (streptococci), cluster of cocci (staphylococci), vibrio (comma shaped), spirillium (spiral), spirochaete (corkscrew)
How do cytokine molecules stimulate specific groups of B lymphocytes?
Cytokines have specific shape complementary to the receptor on the cell surface membrane B lymphocyte. This stimulates clonal expansion.
Define Parasite
Lives in host. Lives off host digesting cell organelles gaining nutrition from this at the expense of the host.
