Immunity Flashcards
Monocolonal antibodies
Each of the plasma cells will produce a different antibody. Such antibodies are known as monoclonal antibodies.
Targeting medication to specific cell types by attaching a therapeutic drug to an antibody
There are more successful methods but this is the most
Monoclonal antibodies are produced that are specific to antigens on cancer cells.
• These antibodies are given to a patient and attach themselves to the receptors on their cancer cells.
• They attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth.
Medical diagnosis
They are important in diagnosing certain cancers. For example, men with prostate cancer often produce more of a protein called prostate specific antigen (PSA) leading to unusually high levels of it in the blood. By using a monoclonal antibody that interacts with this antigen, it is possible to obtain a measure of the level of PSA in a sample of blood. it gives an early warning of its possibility and the need for further tests.
Pregnancy testing
These kits rely on the fact that the placenta produces a hormone called human chorionic gonadatrophin (hCG) and that this is found in the mother’s urine.
Monocional antibodies present on the test strip of a home pregnancy testing kit are linked to coloured particles. If hCG is present in the urine it binds to these antibodies. The hCG-antibody-colour complex moves along the strip until it is trapped by a different type of antibody creating a coloured line.
Ethical uses of monocolonal antibodies
In March 2006, six healthy volunteers took part in the trial of a new monoclonal antibody in London. Within minutes they suffered multiple organ failure, probably as a result of T cells overproducing chemicals that stimulate an immune response or attacking the body tissues. All the volunteers survived,
Monoclonal antibodies have been used successfully to treat a number of diseases, including cancer and diabetes, saving many lives. There have also been some deaths associated with their use in the treatment of multiple sclerosis.
Vaccination passive immunity
Passive immunity is produced by the introduction of antibodies into individuals from an outside source. No direct contact with the pathogen or its antigen is necessary to induce immunity. Immunity is acquired immediately. As the antibodies are not being produced by the individuals themselves, the antibodies are not replaced when they are broken down, no memory cells are formed and so there is no lasting immunity.
Active immunity
Active immunity is produced by stimulating the production of antibodies by the individuals’ own immune system. Direct contact with the pathogen or its antigen is necessary. Immunity takes time to develop. It is generally long-lasting and is of two types:
• Natural active immunity results from an individual becoming infected with a disease under normal circumstances. The body produces its own antibodies and may continue to do so for many years.
• Artificial active immunity forms the basis of vaccination. It involves inducing an immune response in an individual, without them suffering the symptoms of the disease.
The success of. Vaccination depends upon
A suitable vaccine must be economically available in sufficient quantities to immunise most of the vulnerable population.
There must be few side-effects, if any, from vaccination. Unpleasant side-effects may discourage individuals in the population from being vaccinated.
• Means of producing, storing and transporting the vaccine must be available. This usually involves technologically advanced equipment,
• There must be the means of administering the vaccine properly at the appropriate time. This involves training staff with appropriate skills at different centres throughout the population.
• It must be possible to vaccinate the vast majority of the vulnerable population to produce herd immunity.
Herd immunity
Herd immunity arises when a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread within that population.
Why a vaccination may not eliminate a disease
Vaccination fails to induce immunity in certain individuals, for example people with defective immune systems.
• Individuals may develop the disease immediately after vaccination but before their immunity levels are high enough to prevent it.
The pathogen may mutate frequently, so that its antigens change suddenly rather than gradually.
This antigenic variability happens with the influenza virus, which changes its antigens frequently.
Ethics of vaccinations
The production of existing vaccines, and the development of new ones, often involves the use of animals.
• Vaccines have side-effects that may sometimes cause long-term harm.
•? To what extent should individuals be asked to accept risk in the interests of the public health?
HIV
On the outside is a lipid envelope, embedded in which are attachment proteins.
Inside the envelope is a protein layer called the capsid that encloses two single strands of RNA and some enzymes. One of these enzymes is reverse transcriptase, called because it catalyses the production of DNA from RNA - the reverse reaction to that carried out by transcriptase. means that HIV belongs to a group of viruses called retroviruses.
Now HIV replicates
Following infection HIV enters the bloodstream and circulates around the body.
• A protein on the HIV readily binds to a protein called CD4. While this protein occurs on a number of different cells, HIV most frequently attaches to helper T cells
• The protein capsid fuses with the cell-surface membrane. The RNA and enzymes of HIV enter the helper T cell.
• The HIV reverse transcriptase converts the virus’s RNA into DNA.
The newly made DNA is moved into the helper T cell’s nucleus where it is inserted into the cell’s DNA.
• The HIV DNA in the nucleus creates messenger RNA (mRNA), using the cell’s enzymes. This mRNA contains the instructions for making new viral proteins and the RNA to go into the new HIV.
• The mRNA passes out of the nucleus through a nuclear pore and uses the cell’s protein synthesis mechanisms to make HIV particles.
• The HIV particles break away from the helper T cell with a piece of its cell-surface membrane surrounding them which forms their lipid envelope.
How HIV causes symptoms of AIDS
HIV causes AIDS by killing or interfering with the normal functioning of helper T cells. An uninfected person normally has between 800 and 1200 helper T cells in each mm’ of blood. In a person suffering from AIDS this number can be as low as 200 mm-3. HIV does not kill individuals directly. By infecting the immune system, HIV prevents it from functioning normally.
The ELISA test
It uses antibodies to not only detect the presence of a protein in a sample but also the quantity.
Apply the sample to a surface, for example a slide, to which all the antigens in the sample will attach.
• Wash the surface several times to remove any unattached antigens.
• Add the antibody that is specific to the antigen we are trying to detect and leave the two to bind together.
• Wash the surface to remove excess antibody.
Add a second antibody that binds with the first antibody. This second antibody has an enzyme attached to it.
• Add the colourless substrate of the enzyme. The enzyme acts on the substrate to change it into a coloured product.
• The amount of the antigen present is relative to the intensity of colour that develops.
