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The immune system: Part 1

JESSICA MAWU-KOENYA BANSAH
JESSICA MAWU-KOENYA BANSAH

Science states that, out of the microbes(germs) in our environment, only 20% cause infections and less than 1% of bacteria cause diseases. This is shocking due to the numerous diseases in our world. The question is, how do we survive all these? Why don't we fall sick every day since these microbes and pathogens are everywhere? Why does an individual suffer terribly from a disease yet another can manage the disease with ease? The answer has to do with the immune system.

One of the commonest terms used in this era is the “immune system”, not surprising at all. There has been much advice to take good care of the immune system, boost it to increase the efficient response to incoming diseases. With all these suggestions, one may want to know what the immune system is, how it operates, what it looks like, and what influences its mechanism.

‌‌The immune system is an incredible defense system. Just like the notes in a piano or guitar which are played together in chords to produce a harmonious melody. If one note or string is removed, the melody becomes unpleasant to the ear. That is how the immune system also works. Immunity is the protection conferred by the immune system.

It involves a group of cells, molecules and chemicals that work together to protect an individual. If one aspect fails, it might cause devastating effects such as autoimmunity, hypersensitivities or allergies, cancer and inflammation. However, the immune system is sharp in regulating itself to ensure good health. ‌‌It works based on two mechanisms - recognition and response. It can distinguish one foreign pathogen from another. For example, it can distinguish between a pathogen that causes malaria from one that causes cholera. Moreover, it can distinguish between foreign pathogens from the body's own cells and proteins. This happens to avoid attacking the body's own cell. If this happens, it is termed an autoimmune disease.

Once a foreign organism has been recognised, the immune system will mount an appropriate response to eliminate or neutralise the organism just like how soldiers react in war. The human body mounts two main response upon the recognition of a foreign pathogen: Innate and Adaptive immune response.‌‌In this article, we will tackle the Innate immune response.

‌‌Innate immunity refers to all those components with which an individual is born and that are always present to protect the individual from foreign invaders. The innate system is the first line of defense against a foreign agent.

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It contains barriers and elements that prevent infection. Its response is fast as it reacts within minutes to hours after recognising a foreign substance. This type of response is non-specific. Immediately it recognises that a substance is foreign, it jumps onto the foreigner to eliminate it. They are like the bodyguards at the entrance of a building. They come at you with whatever they have without really knowing what you can do so far as you are foreign. Innate immunity comprises four types of defensive barriers.

  1. Anatomic/Physical barrier‌‌ This is the organism's first line of defense against infections as it impedes the entry of pathogens into the body. They are the skin and mucous membranes.

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Surprising, right? Who would've thought that the skin plays a part in the immune system?

‌‌The skin comprises a thin outer layer - the epidermis which consists of tightly packed epithelial cells. This prevents any pathogen from getting into the body. However, a break in the skin resulting from scratches, wounds or abrasion is an obvious route of infection. That is why nurses use alcohol to rub off the skin and plaster to cover wounds to prevent infection. Also, bathing twice a day is recommended to remove all dirt and pathogens that may have stuck on the body during our normal routine. Yet, biting insects such as mosquitoes and ticks may introduce a pathogen into the body as they feed.

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‌‌The skin also comprises an inner thicker layer - the dermis. One important tool is the secretion of sebum by the sebaceous glands of the dermis. This secretes acids that maintain the pH of the skin between 3 and 5. This pH is too acidic for most microbes. Also, our immune system harbor few bacteria that live on the skin. These bacteria called normal flora are not usually harmful. They stay there and use the space and sebum, in case a pathogen is able to survive in the acidic conditions, they will fight it for space and nutrients and eventually overthrow it.‌‌ Amazing, right?

‌‌Mucous membranes

‌‌The respiratory, digestive and urogenital tracts are lined by mucous membranes. Secretions such as saliva, tears and mucus wash away foreign agents and contain antiviral and antibacterial substances. So it is not surprising to hear people say that crying is good as it makes your immune system function.

Furthermore, the viscous nature of the mucus entraps foreign pathogens just like how the police patrols can trap robbers and neutralise their activities.‌‌ The mucous membranes also contain normal flora that competes for attachment sites and nutrients. This is important, especially in the urogenital area. It is good to wash the genitals with clean water but using chemicals to wash the genitals, especially the vagina may cause this normal flora to be removed and may give way to pathogens since they won't compete with any microbes when they land at the genitals. Hence, products such as feminine wash should be avoided, the body has its mechanism of cleaning and keeping the area clean.

2. Physiologic Barriers‌‌

This deals with how the body's functioning protects us from infection. The temperature in our body inhibits the growth of some pathogens. This is easy because humans can't work well in heated environments so the temperature in the body restricts the growth of these microbes.‌‌ The acidity in the stomach kills most ingested microorganisms. This is one trick amongst people who eat from places that could result in infection but still do not fall sick.  Also, newborns have less acid in their stomach so it makes them susceptible to some diseases. That is one reason why breast milk is the preferred meal for a period to avoid infection.‌‌Furthermore, there are chemicals produced by the body such as lysozyme that aids in neutralising pathogens.

3. Phagocytic barriers‌‌

This is an important part of the innate defense system. These contain cells that take up materials from the environment or secrete chemicals that recruit other cells to join them. They usually do this by either engulfing(swallowing) or binding to pathogens, kill and digest the whole microbe.

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4. Inflammation

‌‌Inflammation is painful and many may agree it is harmful but that is the body's way of clearing an invader that may have gotten to body tissue. The inflamed area is made up is dead cells, digested material consisting of bacteria and fluid (enzymes and acids) that aid in the clearance.

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Nonetheless, inflammation may affect other healthy cells around or press on body parts which may cause disruptions.‌‌ Once the inflammation has subsided, tissue repair and regeneration of a new tissue begins.‌‌ Innate immunity is remarkably versatile and important in our protection. So the next time, you think about your immune system, do not think only about vitamins and minerals. Think about your lifestyle and how you can help your immune system to be strong.‌‌ Watch out for the second aspect of the immune system that is complex and present only in mammals in our next article. Thank you!

JESSICA MAWU-KOENYA BANSAH

A young lady who is excited to influence the society and world with the knowledge she has acquired.