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The Immune System - Our Body's First Line of Defense


Inflammation is the body's immediate response to infection.

Our immune system is the body's first line of defense against harmful elements that come in contact with it such as harmful bacteria, viruses, toxins and various pathogens that could seriously harm the body.

It's called a "system" because it is composed of many body organs, body tissues, cells, and various enzymes that work together to protect the body from diseases.

The best way to boost your immune system is to protect the body parts and systems that prevent these pathogens from entering the body.

The body has various protective mechanisms that prevent different kinds of viruses and bacteria from entering and invading it. These mechanisms should be fiercely guarded and protected as they are the body's first line of defense against various kinds of diseases.

Inflammation is the body's immediate response to infection. It is our immune system's reaction to a danger. If you have an inflammation in any part of your body that means your immune system is working to warn you about a potential threat to your health or it is trying to fight off bacteria or germs that has invaded your body.

A very good example of an inflammation that occurs in your body in response to infection is inflammation of the lymph nodes. Your lymph nodes are sensitive and painful. If your infection is on the upper part of your body, the lymph nodes affected are the ones under your armpits

When the infection is on the lower part of your body, the lymph nodes affected are the ones on the thighs. Next time you experience inflammation in your body, observe and notice which lymph nodes are affected.

An overactive immune system can cause diseases such as allergies, asthma, sepsis and various types of autoimmune diseases.

When the body has infection, it responds to the infection by causing an inflammation in the infected area. The signs of inflammation are swelling, redness, the affected area feels hot and painful caused by increased blood flow in the tissues. The inflammation is caused by eicosanoids and cytokines, substances that are released by the infected or damaged cells.

Which body parts and systems should be protected?


Innate Immunity is the kind of immunity that you were born with, the one you acquired when you were still in your mother's womb. It can also be called natural immunity.

Some of the major parts of the body that act as protection against infection are:

  • the skin,
  • the phagocytes which are components of white blood cells,
  • the so-called complement system which is a system of proteins that assist antibodies in removing pathogens; and
  • the interferons.

All these protective barriers belong to one component called the Innate Immune System.

The complement system fights bacteria by producing a hole in the exterior of the cell which eventually leads to cell death or apoptosis.

Phagocytes fight bacteria by surrounding and engulfing them until they are completely destroyed.

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Adaptive Immunity

This is the type of immunity that remembers the first encounter with a pathogen. It is better prepared to confront and fight the same pathogen when it returns to attack the body again. Vaccination is based on this principle of adaptive immunity.

What's the difference between viral and bacterial infection

Bacterial infection is caused by bacteria, those very tiny single-celled microorganisms that have the ability to reproduce rapidly. They have the ability to survive in extremely hot or cold environment, they can survive in environments that have been contaminated by radioactive waste materials, and most importantly, they can thrive well in the human body.

Bacteria are harmless creatures. Less than one percent of them can make people sick. They are in fact useful in digestion, in destroying cancer cells, in supplying the body with needed nutrients, and in destroying microorganisms that cause diseases.

Viral infection is caused by viruses

The Body's Immune System

Chemical protective mechanisms

Chemical barriers from infection include bodily secretions, proteins and fatty acids that possess antibacterial characteristics, low ph, or the ability to destroy harmful bacteria.

Vaginal secretions when they become acidic, prevent bacteria and other harmful microorganisms from entering the body through the vaginal canal.

Semen contains zinc that kill pathogens.

Lysozomes and phospholipase A2 are found in saliva, tears and breast milk to protect them from bacterial invasion.

Gastric juice and proteases protect the stomach from pathogens. Pepsin is an enzyme found in the stomach that detroys various microorganisms.

Hydrochloric acid has the ability to create a stomach environment that is low in ph and can prove hostile to many pathogens.

Mechanical protective mechanisms

The skin and mucus membranes are classified as mechanical barriers. The mucus membrane walls are composed of epithelial tissues attached to cilia that protect the lungs from harmful particles. In some cases, the epithelium is damaged because of smoking making smokers vulnerable to respiratory diseases.

Sneezing and coughing remove pathogenic substances from the respiratory tract. Bacteria and viruses are also expelled from the body through tears and urine while mucus try to trap them when they attempt to enter the body

Since there are body openings that can allow bacteria and other microbes to enter the body, there are parts of the body that protect from infection such as the genitals, the urinary tract, the lungs, and intestines.

Once the lungs are exposed to infection, a very quick response by the innate immune system happens. The dendritic cells and macrophages of the innate immune system readily recognize the enemy as the pathogen-associated molecular patterns or PAMPs. These PAMPs are easily recognized by pattern-recognition receptors which send a message to the cells of the innate immune system to attack and destroy the bacteria.

What is herd immunity?

Herd immunity happens when a group of people or a community - referred to as the "herd" - has acquired immunity to a particular disease and therefore preventing the transmission of the disease. This makes the whole community protected

© 2013 Zee Mercado


Zee Mercado (author) on July 06, 2013:

Thanks a lot! As of today, July 6, 2013, this hub is still a work in progress. I'm still trying to improve the lay out and format.

Joseph Davis from Florida on July 05, 2013:

great and well written hub, excellent choice of topic. Your layout is different, but I like it!

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