SPLATS about immune responses
For an explanation, see
the main splats page
In ancient Greece, Thucydides reported that people who had already experienced the plague were then immune to it, and able safely to nurse other victims.
In complex organisms such as mammals, evolution has favoured an extremely intricate immune system that will attack any cells recognized as 'non-self'.
In complex organisms, there are many ways for cells to identify 'self' and 'non-self', based on the shapes and charges of surface markers on the cell membrane.
Our immune system protects us from materials and organisms recognized by the body as 'foreign', things not known to be a normal part of the body.
Antibodies are part of the immune system, and they generally act by binding to an antigen, changing it so that it can no longer operate as normal.
The presence of particular antibodies in your blood indicates that you have had a previous exposure to particular antigens, typically organisms or toxins.
Immunity can be acquired: immunization with a vaccine stimulates the immune system by providing it with a harmless model of molecules that need to be attacked.
In 1890 Emil Adolf von Behring discovered antibodies and antitoxins, and used this novel principle to develop tetanus and diphtheria vaccines.
A vaccine prepared from weakened or heat-killed disease organisms gives people immunity by preparing the immune system to attack the real thing when it arrives.
A vaccine made from parts of the exterior of disease organisms can give people immunity without infecting them, by preparing the immune system to attack them.
Vaccines against typhoid and cholera were developed in 1896, and they bubonic plague vaccine was available in 1897. All of these used inactivated bacteria.
The Lübeck disaster is a rare example of how vaccination can go wrong: it happened when full-strength TB bacteria were inoculated instead of weakened ones.
As a general rule, there is a small but measurable risk associated with every inoculation. There is a greater risk associated with NOT being inoculated.
Interferons are naturally occurring proteins that are a part of the immune system, operating in a variety of ways to regulate the immune system.
Around 1020, the Arabic scientist Avicenna described diabetes and that the urine of diabetics tastes sweet, after seeing ants attracted to a diabetic's urine.
Occasionally the immune response goes out of control, and attacks part of the host organism by mistake, in what is called an autoimmune reaction.
Our immune system can cause autoimmune disease when it 'makes a mistake': Type I diabetes is an autoimmune disease, probably caused by a bacterium.
Juvenile (type I) diabetes is triggered when an autoimmune response attacks key cells in the pancreas, and destroys them by mistake for an infective agent.
There appears to be a standard pattern for autoimmune diseases, where early exposure to an organism triggers a later mistaken attack on part of the body.
Blood and tissue can be typed, according to the antigens found in a particular blood sample, allowing a closer match for blood and organ donations.
Tissue typing is required before transplantation: organ donations, have a better chance of success when the donor and recipient have similar immune markers.
The immune response can be modified or muted by drugs known as immunosuppressants, but the same effect is also caused by HIV, the human immunodeficiency virus.
Immunosuppressive drugs may be needed for a transplant of an organ from a donor to succeed, even when the match between donor and recipient tissues is good.
In the future, xenografting of organs may be possible, using organs from animals which have been specially prepared to have no immune markers.
One source of xenografts may be pigs, but pig xenografts may carry viruses called porcine endoretroviruses or PERVs, which might infect the recipients.
All multicellular organisms, both plants and animals, have evolved ways of defending themselves against invaders and infections by microorganisms.
The simple immune system of the invertebrates involves producing soluble factors which are more harmful to invaders than they are to the host cell.
The more complex immune system of the vertebrates involves a quick-acting innate system that does not adapt very well and a slower-acting adaptive system.
The adaptive immune system has a memory for attackers which it has encountered before, and it is this memory that make use of when we apply vaccines.
The innate system in vertebrates is much more complex than the invertebrate system, with a variety of factors secreted by different cells in the body.
One group of factors is made of the cytokines, a group of different proteins that are produced and secreted by cells. Another group is the chemokines.
Two main types of cell are involved in the adaptive immune system. These are the two kinds of lymphocytes and the antigen presenting cells or APCs.
B lymphocytes are formed in the bone marrow and travel from there directly to the lymph nodes, while T lymphocytes reach lymph nodes by way of the thymus.
In 1957, Macfarlane Burnet proposed his clonal selection theory of B lymphocytes, suggesting that each B cell has antibody receptors to a unique antigen.
Macfarlane Burnet's theory was ridiculed at the time, but it now lies at the very centre of our understanding of immunology and the immune system.
When an antigen matching the specificity of a B cell appears, more copies of that lymphocyte are produced, resulting in strong antibody production.
A small number of people persist in arguing that vaccination is dangerous. Nothing is ever free of risk, it is far more dangerous to refuse to be vaccinated.
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