Immune System and Foreign Invaders
Evolutionary origin of bacteria and viruses
Earth formed between 4.5 and 6 billion years ago. Conditions initially remained inhospitable for the potential development of life. By about 3.0 billion years ago, however, an atmosphere that contained the appropriate blend of nitrogen, oxygen, carbon, and hydrogen allowed life to commence. The formation of proteins and nucleic acids led to the generation of the genetic code , contained in deoxyribonucleic and ribonucleic acids, and the protein machinery to translate the information into a tangible product.
Fossil evidence indicates that one of the first life forms to arise were bacteria . The planetary conditions that were the norm four to six billion years ago were much different from now. Oxygen was scarce, and extremes of factors such as temperature and atmospheric radiation were more common than now. Although the exact origin of bacteria will likely never be known, the present-day bacteria that variously tolerate extremes of temperature, salt concentration, radiation, pH and other such environmental factors may be examples of the original bacteria.
“Tracing the origins of viruses is difficult because they don’t leave fossils and because of the tricks they use to make copies of themselves within the cells they’ve invaded. Some viruses even have the ability to stitch their own genes into those of the cells they infect, which means studying their ancestry requires untangling it from the history of their hosts and other organisms. What makes the process even more complicated is that viruses don’t just infect humans; they can infect basically any organism—from bacteria to horses; seaweed to people.”
– Ed Rybicki, a virologist at the University of Cape Town in South Africa
Still, scientists have been able to piece together some viral histories, based on the fact that the genes of many viruses—such as those that cause herpes and mono—seem to share some properties with cells’ own genes. This could suggest that they started as big bits of cellular DNA and then became independent—or that these viruses came along very early in evolution, and some of their DNA stuck around in cells’ genomes. The fact that some viruses that infect humans share structural features with viruses that infect bacteria could mean that all of these viruses have a common origin, dating back several billion years. This highlights another problem with tracing virus origins: most modern viruses seem to be a patchwork of bits that come from different sources—a sort of “mix and match” approach to building an organism.
Viruses and bacteria
Viruses are too small to be seen by the naked eye. They are not able to multiply on their own. They have to invade a “host” cell and take over its machinery in order to be able to make virus particles.
Viruses consist of genetic materials (DNA and RNA) surrounded by a protective coat of protein. They are capable of latching onto cells and getting inside them.
The cells of the mucous membranes, such as those lining the respiratory passages that we breathe through, are particularly open to virus attacks because they are not covered by protective skin.
Bacteria are mono-cellular organisms. They are capable of multiplying by themselves, as they have the power to divide. Their shapes vary, and doctors use these characteristics to separate them into groups.
Bacteria exist everywhere, inside and on our bodies. Most of them are completely harmless and some of them are very useful.
But some bacteria can cause diseases, either because they end up in the wrong place in the body or simply because they are “designed” to invade us.
Your body has an amazing internal defense mechanism called the immune system. His role is to protect you from bacteria and viruses that can lead to illness.
Now back to our immune system, his role is to produce a variety of different cells to attack the invading bacteria and viruses.
Your blood contains many different types of cells. Red blood cells carry oxygen to all the parts of your body. Platelets stop bleeding by helping with blood clotting. White blood cells, known as leukocytes, make up the immune system portion of the blood.
Leukocytes are divided into three main groups:
Granulocytes – these are cells which contain granules which contain chemicals that are used to kill bacteria and viruses
Lymphocytes– these are cells which attack most of the bacterial and viral infections in our bodies
Monocytes– these are cells which become macrophages, large cells that engulf harmful particles in our bodies.
These three types of leukocytes are even further divided into more specialized cells, each with their own unique task in the immune system.
Immune system knows which cells are part of our body and which are not.
Your immune system can recognize cells based on the proteins present on the surface of cells. Viruses, bacteria, and other foreign cells are recognized as being different from your own cells and are attacked by your immune system. Sometimes, one of your own cells changes, or mutates, giving the cell the ability to multiply continuously. Such mutations often are the cause of cancer. Your immune system has the ability to recognize cells and attack them before they can grow into a tumor.
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Immune System is not foolproof
Despite the amazing ability to protect your body, the immune system is not an invincible defense. Certain viruses can outwit your immune system (HIV). Also, genetic malfunctions can result in an ineffective immune system (lupus).
The spreading of the viruses and bacteria
The spreading of viral and bacterial infections are basically the same:
- A person with a cold can spread the infection by coughing and/or sneezing.
- We “share” bacteria or viruses by touching or shaking hands with another person.
- Touching food with unwashed hands will also allow viruses or bacteria from the intestine to spread.
- Body fluids, such as blood, saliva and semen, can contain the infecting organisms and transmission of such fluids, for example by injection or sexual contacts, is important, particularly for viral infections like hepatitis or AIDS.
Tips to prevent infections:
- Wash your hands thoroughly, because this is one of the best ways to avoid infections
- Shaking hands with someone who has a cold is risky, if you try to rub your eyes or nose afterwards
- Store your vegetables and meat separately and prepare them on separate chopping boards.
- Meat should be preferably served well-done.
- Remember that these invisible organisms does not have a bad smell
- Some organisms are killed while they are cooked, but they can still leave toxic substances that may cause diarrhea and vomiting.
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