Infection and response 2 Flashcards
Defence systems, Monoclonal antibodies, Medicine.
What non-specific defence systems does the human body use to prevent pathogens from getting in?
-Skin
-Mucus in nose, trachea, and bronchi
-Cilia in the trachea and bronchi
-Stomach acid
How does the skin stop pathogens?
-It’s a physical barrier
-It secretes antimicrobial substances which kill pathogens
How do cilia stop pathogens?
Move the mucus up to the back of the throat where it can be swallowed
How does mucus stop pathogens?
Trap particles that could contain pathogens
How does the stomach prevent pathogens making us ill?
Produces hydrochloric acid which has a low pH of 2, killing pathogens.
What is the role of the immune system?
To destroy a pathogen if it enters the body.
What is the most important part of the immune system?
The white blood cells
What is the function of white blood cells?
-Phagocytosis to destroy pathogens
-Producing antitoxins to counteract toxins released by pathogens
-Producing antibodies to destroy specific pathogens
What is an antitoxin?
A substance that neutralises toxins produced by pathogens (bacteria) by binding to them.
What are antibodies?
-Small y-shaped proteins that bind to specific foreign antigens on the surface of pathogens
-This signals our immune system to destroy the pathogen
-Produced by Lymphocytes
What are memory cells?
The WBCs which remember how to make specific antibodies.
What is the secondary immune response?
The second time the body is exposed to a specific antigen, WBCs will produce antibodies much faster and in greater numbers than before.
So, they destroy the pathogen (hopefully) before a person develops symptoms - this is known as immunity.
This is because memory cells remember how to make the specific antibodies for that antigen.
What is the first response to an infection and why?
A fever. The higher temperatures denature pathogen enzymes, slowing the pathogen down.
However, normal enzymes will also be denatured making us feel ill.
What happens during phagocytosis?
A phagocyte goes to the area of infection and engulfs a pathogen, which it recognises as foreign. It then releases enzymes to digest the pathogen.
What is an antigen?
A specific protein found on the surface of a pathogen.
What does a vaccination contain?
A small amount of the dead or weakened form of a pathogen.
How does a vaccine work?
-Vaccination involves injecting a small amount of the dead/weakened/ inactive form of a pathogen into the body.
-White blood cells will produce specific antibodies
-Memory cells are produced and remain in the body
-If reinfected your white blood cells can quickly produce the correct antibodies and in higher quantities (secondary immune response)
-The pathogen is destroyed before it had the chance to reproduce/cause symptoms (immunity)
How can the spread of pathogens be reduced by immunising a large proportion of the population?
Even people who aren’t vaccinated are unlikely to catch the disease because there are fewer people available to pass it on. This is known as ‘herd immunity’.
Briefly explain the process of vaccination.
Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies.
If the same pathogen re-enters the body, the white blood cells respond quickly to produce the correct antibodies, preventing infection.
Pros of vaccination
-You can control communicable diseases that were once common, e.g. smallpox
-You can prevent epidemics via herd immunity
What may happen if a significant number of people aren’t vaccinated?
A disease can spread quickly through them and lots of people can become ill at the same time.
Cons of vaccination
-Vaccines don’t always work/give people immunity
-You can sometimes have a bad reaction to a vaccine.
Specific bacteria should be treated by…
…specific antibiotics because different ones kill different types of bacteria.
Why are antibodies a specific defence?
Antibodies have unique shapes so are complementary to a specific pathogen’s antigens.
Hence they target specific pathogens.
What are painkillers?
Drugs that reduce the symptoms of a disease but do not kill pathogens.
-Other drugs can do this to e.g. ‘cold remedies’
What are antibiotics?
Medicines that help to cure bacterial disease by killing (or preventing the growth of) infective bacteria inside
the body - without killing body cells.
Why can’t antibiotics kill viral pathogens/be used to treat viral diseases?
Viruses reproduce using you body cells which makes it difficult to develop drugs that destroy just the virus without killing the body’s cells.
What has the use of antibiotics done?
The use of antibiotics has greatly reduced the number of deaths from infectious bacterial diseases.
How do strains of bacteria become resistant to antibiotics?
Bacteria can mutate and sometimes these mutations cause them to be unable to be killed an antibiotic (resistant).
Why is the emergence of bacterial strains resistant to antibiotics of concern?
-When you treat an infection with antibiotics, only non-resistant strains of the bacteria will be killed
-The resistant bacteria will survive and reproduce by binary fission
-The population of the resistant strain will increase
-The resistant strain could cause a serious infection that can’t be treated by antibiotics
How can we slow the development of resistant strains of bacteria?
-Doctors shouldn’t over prescribe antibiotics
-Finish the whole course of antibiotics
What is Digitalis?
-A drug used to treat heart conditions
-It was developed from a chemical in/originates from foxgloves (plant)
What is Aspirin?
-A painkiller, also used to lower fever
-It was developed from a chemical found in willow
Why are many drugs extracted from plants?
-Plants produce a variety of chemicals to defend themselves against pathogens
-Some of these chemicals can be used to treat human diseases or relieve symptoms
What is Penicillin?
-The first antibiotic
-Discovered by Alexander Fleming from the Penicillium mould
How did Alexander Fleming discover penicillin?
-He was cleaning out petri dishes with bacteria on
-One with mould on it had a clear zone around the bacteria
-He found that the mould was producing a substance that killed the bacteria- Penicillin.
How are most new drugs made now?
Most new drugs are synthesised by chemists in the pharmaceutical industry.
However, the starting point may still be a chemical extracted from a plant.
What are new drugs tested for?
-Toxicity
-Efficacy
-Dosage
what are the three main stages in drug testing?
-Preclinical testing of drugs on human cells and tissues in a lab
-Preclinical testing of drugs on live animals
-Clinical testing/trials on first healthy volunteers, and then on patients suffering from the disease
Where is preclinical testing done and what with?
Preclinical testing is done in a laboratory using cells, tissues and live animals.
What are clinical trials?
The final big stage in drug testing.
Clinical trials use healthy volunteers and patients to test drugs.
Why might a computer simulation be helpful in pre-clinical testing?
You can predict how a drug might react with a target.
What is the main purpose of pre-clinical testing?
Testing for toxicity to see if the drug is safe.
What is the purpose of tissue and organ testing?
Tests how the drug affects human cells or tissues to rule out it being toxic.
What is the purpose of animal testing?
To test:
Efficacy - whether the drug works and produces the effect you’re looking for
-Toxicity -what side effects it may cause in a whole organism
-Dosage - at what concentration and frequency the drug is most effective
What is the purpose of initial clinical trials on healthy people?
Drugs are tested on healthy volunteers to make sure they doesn’t have any harmful side effects when the body is working normally (even in low doses - this is gradually increased).
What is the purpose of clinical trials on patients?
To find the optimum dose (the dose at which the drug is most effective and has the fewest side effects).
What is the purpose of large clinical trials on patients?
-To test if the drug is effective for a wide range of different people
-To further track side effects
-To find the optimum dose
What is a placebo?
A fake treatment with no active compound (medicine) in it.
What is a double-blind trial?
Where neither the doctor, nor the patient knows which treatment is the placebo.
Why might a placebo be given to a control group?
-So that the doctor can see the actual difference a drug makes (test it’s efficacy, it has to make a big difference for the treatment to be proved effective)
-It allows for the placebo effect (where the patient feels better because they expect a drug to work, even though the treatment isn’t doing anything)
Why are clinical trials often double-blind?
-Neither the patient or the doctor know which patients are receiving the drug vs the placebo
-So the doctors monitoring the patients and analysing results aren’t subconsciously influenced by their knowledge
Only after peer review can…
…results of testing and trials be published. (this helps prevent false claims).
What type of molecule is an antigen?
A protein
Explain how monoclonal antibodies can target a specific chemical/specific cells in the body.
Monoclonal antibodies are produced by clones of a single hybridoma, which is made from a tumour and B-lymphocyte (WBC).
The B-lymphocyte produces specific antibodies which are complementary to the binding site of one type of protein antigen.
So the antibodies produced by the clones also produce these specific antibodies.
How are monoclonal antibodies produced? (steps 1 and 2)
-A mouse is injected with a pathogen/specific antigens
-This stimulates mouse lymphocytes to make a specific antibodies (which target the specific protein antigens)
How can monoclonal antibodies be used?
-for diagnosis such as in pregnancy tests
-in laboratories to measure levels of hormones and other chemicals in blood
-in labs to detect pathogens
-in the treatment of some diseases, e.g. cancer
-in research to locate or identify specific molecules in a cell or tissue by binding to them with a fluorescent dye
How can monoclonal antibodies be used to treat cancer?
The monoclonal antibody can be bound to a radioactive substance, a toxic drug, or a chemical which stops cells from growing and dividing.
It delivers the substance directly to the cancer cells without harming other cells in the body.
This is because only cancer cells have ‘tumour markers’ (antigens on their cell membranes which the antibody will bind to) so only these cells are targeted.
What is a hybridoma cell?
A hybrid of a lymphocyte and a tumour cell, which is both fast dividing, and can produce antibodies that are complementary to the antigens of a specific chemical or cell.
How does the control strip on a pregnancy test work and why do we have it?
-Free antibodies bind to the control area
-The control strip will turn blue indicating the pregnancy test works correctly.
What is a clone of cells?
A group of identical cells that have formed from a single cell, which has repeatedly been divided.
How are monoclonal antibodies used in diagnostic testing?
They are used to measure levels of hormones or chemicals in the urine or blood e.g. hCG in the urine to test for pregnancy
How are monoclonal antibodies used in laboratories and research to find specific substances?
-First, monoclonal antibodies are made which will bind to the specific molecules you’re looking for
-The antibodies are then bound to a fluorescent dye
-If the molecules are present in the sample you’re analysing, the fluorescent monoclonal antibodies will bind to antigens on the sample
-So any specific substances present in the sample will be detected using the dye.
Monoclonal antibodies bind to…
…a specific surface antigen.
Advantages of monoclonal antibodies
If used in cancer treatment, they have less side effects than standard chemotherapy or radiotherapy.
This is because monoclonal antibodies target specific cells so don’t damage normal body cells.
Disadvantages of monoclonal antibodies
-Cause more side effects than originally expected (e.g. fever, low blood pressure)
-So not used as treatments as widely as anticipated
Ethical issues involved in producing monoclonal antibodies
The mice are often killed, as their spleen is removed to extract the B-lymphocytes.
How can plant diseases be detected?
- stunted growth
- spots on leaves
- areas of decay (rot)
- growths
- malformed stems or leaves
- discolouration
- the presence of pests.
How can plant diseases be identified?
- reference to a gardening manual or website
- taking infected plants to a laboratory to identify the pathogen
- using testing kits that contain monoclonal antibodies.
How can plants be infected?
By a range of viral, bacterial and fungal
pathogens as well as by insects (infestations).
How can aphids (greenflies) be controlled by gardeners?
-Use pesticides
-Introduce a natural predator (like ladybirds) to eat them
Plants need mineral ions from the soil. If there aren’t enough, plants…
…suffer from deficiency symptoms
What does a nitrate deficiency cause? (plants)
Stunted growth
(as nitrate ions are needed for protein synthesis, and therefore growth)
What does a magnesium deficiency cause? (plants)
Chlorosis (insufficient chlorophyll)
The understanding of ion deficiencies allows…
…horticulturists to provide optimum conditions for plants.
Physical defence responses in plants to resist invasion of microorganisms:
- Cellulose cell walls
- Tough waxy cuticle on leaves
- Layers of dead cells around stems (bark on trees) which fall off.
Chemical plant defence responses:
- Antibacterial chemicals (that kill bacteria, e.g. from witch hazel)
- Poisons to deter herbivores (e.g. from foxgloves, deadly nightshade).
Mechanical adaptations of plants:(defences)
- Thorns and hairs deter animals.
- Leaves which droop or curl when touched. (allows the leaf to move away from things and knock insects off)
- Mimicry to trick animals
What happens in clinical trials?
- Very low doses of the drug are given at the start of the clinical trial.
- If the drug is found to be safe, further clinical trials are carried out to
find the optimum dose for the drug. - In double blind trials, some patients are given a placebo
How are monoclonal antibodies produced? (steps 3 and 4)
-The lymphocytes are extracted by removal of the mouse’s spleen and combined with a specific type of tumour cell (from the lab) to make a cell called a hybridoma cell.
-The hybridoma cell is both fast dividing and capable of making the specific antibodies.
How are monoclonal antibodies produced? (steps 5, 6, and 7)
-Single hybridoma cells are cloned to produce many identical cells that all produce the same antibody.
-These are known as monoclonal antibodies.
-A large amount of the antibody can be collected and purified.
Why does chlorosis lead to yellow leaves?
Magnesium ions are needed for making chlorophyll, the green pigment which is needed for photosynthesis, a lack of which means plants who suffer chlorosis have yellow leaves.
Mimicry (mechanical plant defence)
Plants mimic other organisms
For example, passion flowers have spots which look like butterfly eggs to trick butterflies from laying there.
Plants can mimic other organisms to…
… prevent being eaten.
What is hCG?
A hormone which is excreted in their urine of pregnant women.
Give uses of monoclonal antibodies.
-pregnancy testing
-to diagnose some cancers
-to locate blood clots
-to identify specific molecules
Explain how pregnancy test strips work to show a positive result. (steps 1 and 2)
-As urine passes through the reaction zone, HCG hormone binds to the mobile HCG antibody
-HCG hormone binds to the immobilised HCG antibodies in the results zone
Explain how pregnancy test strips work to show a positive result. (steps 3 and 4)
-Antibodies which do not bind to HCG bind to antibodies in the control zone
-Blue dye appears in both the control and results zones to show a positive result
