B6 preventing and treating disease Flashcards
What are painkillers?
Painkillers
are chemicals that relieve the symptoms but do not kill the pathogens. Common examples include paracetamol and aspirin, and they can relieve a headache or a sore throat.
As the symptoms are treated, your immune system still needs to combat the pathogen.
What are antibiotics?
Antibiotics are substances that slow down or stop the growth of bacteria. They are commonly prescribed medicines, examples include penicillin and amoxicillin. These can be taken to cure the disease by killing the pathogen, but only cure bacterial diseases and not viral ones.
What is herd immunity?
Following a vaccination, a person can become immune to the specific
disease. This immunity gives protection against illness in an individual. The majority of the population must be vaccinated against serious diseases, which can reduce the chance of people coming into contact with specific pathogens, leading to herd immunity.
What are the three scenarios with herd immunity?
The majority of the population are not vaccinated against a specific disease, however, a few people are ill and contagious. This can develop easily into a mass infection because the majority of the population are not vaccinated.
Most of the population are not vaccinated against the specific disease but are well, some are vaccinated and healthy, and a few are not vaccinated, but ill and contagious. Mass infection can result again, but a small number of vaccinated individuals remain healthy and some that are not vaccinated will also be healthy.
The majority of the population are vaccinated and healthy against a specific disease, a few are not vaccinated but well. A few are not vaccinated against the disease, and they are ill and contagious. The result is that the majority are protected due to the high level of vaccination. A few individuals will still become ill, but the large number of vaccinated individuals gives protection.
What is vaccination?
Pathogens
are microbes that cause
diseases. Vaccines allow a dead or altered form of the disease causing pathogen to be introduced into the body, which contain a specific antigen. This causes the immune system, specifically the
white blood cells, to produce complementary
antibodies, which target and attach to the antigen. When a white blood cell engulfs and digests a pathogen it is called phagocytosis.
What happens after vaccination?
During the
primary infection
the antibodies slowly increase, peak at around ten days and then gradually decrease. A second exposure to the same pathogen causes the white blood cells to respond quickly in order to produce lots of the relevant antibodies, which prevents infection.
How are drugs extracted from plants?
Certain drugs can be extracted from natural sources, and have been known about for a long time. For example, willow bark was used by the ancient Greeks to help cure fevers and pains. It was later discovered that the active ingredient was salicylic acid. This was modified by chemists into the substance we call aspirin, which is less irritating to the stomach than salicylic acid. Another example is the heart drug, digitalis which is extracted from foxgloves.
Plants are still important today, but most plant drugs are now created in a laboratory by scientists at
pharmaceutical
companies. These companies now have
synthetic
versions of the plant extracts, and use these as the starting point to develop new drugs.
New medical drugs have to be tested to ensure that they work, and are safe, before they can be prescribed.
What is thalidomide and its legacy?
Thalidomide is a medical drug that caused unexpected and serious damage to unborn babies in the 1950s and 1960s. Thalidomide was developed as a sleeping pill, but it was also thought to be useful for easing morning sickness in pregnant women. Unfortunately, it had not been tested for use in this way.
By 1960 thalidomide was found to damage the development of unborn babies, especially if it had been taken in the first four to eight weeks of pregnancy. The drug led to the arms or legs of the babies being very short or incompletely formed. More than 10,000 babies were affected around the world. As a result of this disaster, thalidomide was banned. Drug testing was also made more rigorous than before.
What are new drugs checked for?
New drug need to be tested and trialled before doctors prescribe them and patients take them. This allows drugs to be checked for:
safety
effectiveness
dosage
What are the stages of testing drugs?
The drugs are tested using computer models and skin cells grown using human stem cells in the laboratory. This allows the efficacy and possible side effects to be tested. Many substances fail this first test of a preclinical drug trial because they damage cells or do not seem to work.
Drugs that pass the first stage are tested on animals in the second part of a preclinical drug trial. In the UK, new medicines have to undergo these tests. But it is illegal to test cosmetics and tobacco products on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects.
Drugs that have passed animal tests are used in human clinical trials. They are tested on healthy volunteers to check that they are safe. The substances are then tested on people with the illness to ensure that they are safe and that they work. Low doses of the drug are used initially, and if this is safe the dosage increases until the optimum dosage is identified.
What are placebos and the blind/doubleblind trials?
The
placebo
effect occurs when someone feels they are better when they have been given a dummy form of the drug, not the drug itself.
To reduce the placebo effect in drug testing:
in
blind trials
only, the doctor knows which patients have been given the drug and which have been given the placebo
in
double blind trials
, neither the doctor nor the patient knows who has been given the drug or placebo
What are monoclonal antibodies?
‘Mono’ means ‘one’ and ‘clone’ means ‘identical copy’.
Monoclonal antibodies
are identical copies of one type of antibody.
Antibodies are proteins produced by a type of white blood called lymphocytes. Pathogens
have proteins on their surface called
antigens. When a pathogen infects the body, the lymphocytes recognise these antigens as foreign
and attack them by producing antibodies.
Antibodies bind to specific antigens on pathogens. This means that only one type of antibody will bind to a matching antigen. Scientists discovered that we could make antibodies to bind to antigens on other substances, and not just those on pathogens. Once bound, the antigens - and the substances they are found on - are merged tightly together. This makes them easier to identify and deal with.
How are monoclonal antibodies formed?
An antigen is injected into a mouse
The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen
Spleen cells which produce the lymphocytes are removed during a small operation
The spleen cells are fused with human cancerous white blood cells called
myeloma cells
to form
hybridoma cells
which divide indefinitely
These hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen
How do monoclonal antibodies help pregnancy diagnosis?
Pregnancy test kits use
monoclonal antibodies. These have been designed to bind with a hormone called HCG which is found only in the urine of pregnant women. Monoclonal antibodies are attached to the end of a pregnancy test stick onto which a woman urinates. If she is pregnant, HCG will be present in her urine and will bind to the monoclonal antibodies on the test stick. This will cause a change in colour or pattern which will indicate pregnancy. These specific monoclonal antibodies in the pregnancy test will only bind with HCG.
How can monoclonal antibodies be used for treating cancer?
Cancerous cells have antigens. Monoclonal antibodies can be designed to bind specifically with these antigens. When injected into a person’s body, the monoclonal antibodies will bind with these cancer cells and clump them together. This makes it easier to identify a cancerous tumour, which can then be treated or removed.
Monoclonal antibodies have also been designed to treat cancer by:
carrying drugs that have been attached to them, to the tumour
encouraging your
immune system
to attack the cancer cells directly
