Immunity is Life (Part I)


Why do I get infections and how does my body fight them?

By using common sense and your five senses you must be careful about where you go and what you do so as not to suffer serious injury.   Your body’s ability to stop bleeding and heal itself is usually enough to keep you going.  But living in the world also means that your body must also defend itself from enemies it can’t detect with its senses nor avoid by running from.  You’re always being exposed to micro-organisms, like bacteria, viruses and fungi that are too small to be seen with the naked eye.  Clinical experience shows that if these microbes infect the body and become widespread, then serious disease, permanent disability and even death can take place. 

Infections can occur in almost every organ of your body.  If your lungs get infected from bacterial pneumonia it can reduce their ability to bring in enough oxygen and get rid of enough carbon dioxide which can lead to respiratory failure and death.  If your gastrointestinal system gets infected from viral gastroenteritis the reduction in oral intake and associated vomiting and diarrhea can lead to a severe loss of water causing dehydration, chemical imbalance and death.  If your brain gets infected from fungal meningitis the loss of central nerve function can cause weakness and confusion leading to coma and death.  I think you get the message loud and clear.

When it comes to microbial attack, just like a medieval town, your body has a two-pronged defensive strategy.  First, just like having a wall and moat with various obstacles as a passive barrier to invasion, your body has specialized cells (epithelium) on the surface of your skin and lining your respiratory, gastrointestinal and genitourinary tracts which act as a passive barrier to microbial entry.  If the invading micro-organisms breach this first line of defense, entering into the tissues below, then the second line of defense, the immune system, consisting of different cells and proteins, swings into action to try to destroy them just like the defenders of the town.

In times gone by when invaders breached the defenses of a town, by using their weapons and shields for protection, the intruders would maim and kill to loot and conquer it.  Similarly, after breaching a passive barrier like your skin (usually through a scrape or cut) or your respiratory system, invading microbes can loot your body by using the nutrients within its fluids or live and grow within its cells.  So, as opposed to a town being stormed by a finite amount of attackers a microbial infection usually involves a small invading force that, once inside the body, can rapidly multiply by using the resources of its host.  It’s the job of your immune system to limit the spread of microbial infection in your body to preserve organ function and allow you to live.

There are many different types of bacteria, viruses and fungi, and the few that have developed the ability to breach your first line of defense and do battle with your immune system are called pathogens.  If the pathogens aren’t stopped within the tissues by which they gain entry into your body (e.g. skin, respiratory system), they can migrate into your lymph vessels.  The lymphatic system consists of very thin walled tiny channels that carry lymph, a liquid that comes from the fluid not brought back into the veins at the end of the capillary.  Every tissue and organ in your body is drained by lymph vessels which eventually all drain into the venous system.   It’s through your lymphatic system that the invading microbes can gain access to your bloodstream and through it all of the other tissues and organs of your body.  This can cause a life-threatening condition called septic shock and death for a quarter of a million people in the U.S. every year.

It’s important to note here that clinical experience shows that for our earliest ancestors to have survived long enough to reproduce they would have had to have had this two-pronged defensive system.  For, neither the passive barriers that protect the underlying tissues, nor the immune system, are capable, on their own, of protecting the body from life-threatening infection.  They both have to be present and working properly for the body to survive within nature.

Three Questions for Mr. Darwin

    1. How did my body anticipate its need to protect itself from microbial invasion by making passive barriers like epithelial cells on the surface of my skin and lining my respiratory, gastrointestinal and genitourinary tracts and where did this information come from?

    2. How did my body know that just having passive barriers to microbial invasion, although vital for survival, would not be enough and where did the information come from to tell it how to make the different cells and proteins that make up my immune system?

    3. Where did the information come from that tells the different cells and proteins of my immune system which cells in my body are foreign invaders in need of destruction and which are part of my body that should be left alone?  

 


Also see Dr. Glicksman's Series on

"Beyond Irreducible Complexity"

"Exercise Your Wonder"


Howard Glicksman M. D. graduated from the University of Toronto in 1978. He practiced primary care medicine for almost 25 yrs in Oakville, Ontario and Spring Hill, Florida. He now practices palliative medicine for a Hospice organization in his community. He has a special interest in how the ethos of our culture has been influenced by modern science’s understanding and promotion of what it means to be a human being.

Comments and questions are welcome.

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