B6: Preventing and treating disease
6.1: Vaccination
Dead or inactive forms of a pathogen are used to make a vaccine - vaccines can be injected into the body (the process is called vaccination/immunisation)
The white blood cells react by producing antibodies, as they would if you were infected by a live pathogen
This response makes the person immune - it prevents subsequent infection because if the body meets this pathogen, it responds quickly by producing more antibodies
Specific antibodies recognise a particular antigen (usually a protein shape) on the pathogen
The MMR vaccine prevents measles, mumps, and rubella - it's one of the vaccines given to children and young people, to protect them and the population
Most people in a population need to be vaccinated to protect society from very serious diseases - this is known as herd immunity
6.2: Antibiotics and painkillers
Antibiotics kill infective bacteria in the body - they destroy the bacteria without damaging the body cells - antibiotics cannot be used to treat viral diseases
Some antibiotics kill a wide range of bacteria - other antibiotics are specific to particular bacteria or types of bacteria
Viruses are difficult to kill because they reproduce inside the body cells, so any treatment for viral infections could also damage the body cells
Painkillers and some other drugs treat the symptoms of a disease but do not kill the pathogen - they're often used to treat the symptoms of viral diseases
Your immune system will usually overcome the viral pathogens
Strains of bacteria have evolved that are resistant to some or all of the available antibiotics - this means the antibiotics cannot kill the bacteria and the disease cannot be cured
Scientists need to find new drugs to kill the antibiotic-resistant bacteria
6.3: Discovering drugs
Many drugs still used today were extracted from plants or microorganisms
Penicillin is an antibiotic that was found in the mould Penicillium - it was discovered by Alexander Fleming but developed by other scientists as an antibiotic
Scientists in the pharmaceutical industry often use chemicals extracted from plants or fungi to develop new drugs
Digitalis and digoxin are drugs extracted from the foxglove plant
Digoxin is still used to strengthen the heartbeat, alongside more modern drugs
Aspirin was first prepared from a compound found in the bark of the willow tree
Scientists are hoping that microorganisms in the soil might reveal new antibiotics to kill antibiotic-resistant bacteria
6.4: Developing drugs
Scientists test large numbers of substances to see if they might cure a disease or relieve symptoms
Researchers test new drugs to make sure they are effective, safe, stable, and can be taken into the body and removed easily
Preclinical testing is carried out in labs on cells and tissues or organs
If the drug seems to work then it's tested on animals
Clinical trials then take place on healthy human volunteers and finally on patients
Healthy people are given very low doses of the drug to find out if it's safe
In some trials with patients, a placebo is used - a placebo doesn't contain a drug
Some patients have the drug, and some the placebo - this is to check that the drug being tested really does have an effect on the patient
6.5: Making monoclonal antibodies
Monoclonal antibodies are a form of medical treatment that relies on the immune system
Monoclonal antibodies are proteins - if all the antibodies come from one type of cell, they are monoclonal
Some white blood cells (lymphocytes) make antibodies naturally, but cannot divide so they cannot be used to produce the antibodies to make medicines
Tumour cells don't usually make antibodies, but they can divide rapidly to make a clone of cells
Stages in making monoclonal antibodies
Mouse lymphocytes are stimulated to make a particular antibody
Scientists combine a mouse lymphocyte with a tumour cell to make a hybridoma
They're monoclonal because they're produced from a single clone of cells
Single hybridoma cells divide to make a large number of identical cells that all produce the same antibodies
These antibodies are collected and purified
Monoclonal antibodies are produced to target particular cells or chemicals in the body
Using monoclonal antibodies
Pregnancy tests rely on monoclonal antibodies that bind to a hormone produced in early pregnancy
Monoclonal antibodies are used to diagnose disease - specific antibodies are produced that bind to the antigens on a pathogen or on a particular type of cancer cell
Monoclonal antibodies are also used to measure and monitor the levels of hormones and other chemicals in the blood for diagnoses in hospitals
In research, scientists can locate specific molecules in a cell by adding fluorescent markers to a monoclonal antibody
Monoclonal antibodies are used to treat diseases
6.6: Uses of monoclonal antibodies
Some have been developed to target specific antigens on certain cancer cells
The monoclonal antibody could carry radioactive substances, a toxic drug, or another chemical directly to the cancer cells without damaging other body cells
Some can trigger the immune system to recognise and destroy cancer cells
Some can block receptors on the surface of cancer cells to stop them dividing
The main advantage of using monoclonal antibodies is that they target specific diseased cells without damaging healthy cells - in conventional cancer treatment the drugs and radiotherapy also damage healthy cells
Disadvantages of using monoclonal antibodies
Side effects - it is hoped that using human cells in hybridomas will reduce these
They are expensive to produce