The Human Immune System

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The word “Infection” comes from a Latin word meaning ‘to be stained’ or ‘to be poisoned’. We now know that infection is not a poison per se, but rather occurs when our bodies are invaded by tiny organisms collectively known as “pathogens”, primarily: bacteria, viruses and fungi. The human body has a multitude of both simple and complex mechanisms to destroy these invaders, but first we must know they are there. By the time we are coughing profusely or losing our lunch, it is late in the infection process. The invaders have moved in and are multiplying.

ANCIENT IMMUNITY: As early as 400 BC Greek General and historian Thucydides made the observation that those who ministered to the sick during times of plague did not themselves become infected. Though what caused these infections still remained unknown. Dutch scientist Van Leuwenhoek announced in 1676 that he had used his microscope to discover tiny life forms, today called bacteria.

SMALLPOX IMMUNIZATION: Smallpox as an infectious disease was described as early as 622 AD by the Egyptian Ahrun, however mummy evidence indicates the disease itself was present in Egypt as early as 2000 BC.
In the mid 1600’s Chinese Emperor K’ang recognized that he had survived a bout with smallpox while his father had not. He recommended the inoculation of small amounts of the infectious agent under the skin as a process to protect others from a fatal course of the disease. The Chinese had been aware of the power of inoculation as early as 10th century AD when inoculation via an intranasal route was a secret practice. Emperor K’ang’s widespread epidemiology program for his people was successful. Traders introduced the practice to the West.

The wife of an English ambassador in Turkey brought the inoculation process to England in 1721. At the time about 60% of the population became infected with smallpox and 20% died from it. English doctor Edward Jenner experimented with vaccination in 1796, which consisted of using fluid from his cow Blossom’s blister (cowpox) instead of from human smallpox, to produce the immunity. During the American War of Independence in the late 1700’s, General George Washington ordered the performance of inoculation against smallpox for his army troops. In the mid 1800’s French scientist Louis Pasteur developed his “germ theory” postulating that infections were caused by the same tiny organisms seen in the Van Leuwenhoek microscope two centuries earlier. Previously the infection’s cause was believed to be foul vapors or perhaps the devil.

Nevertheless, an inoculation program, sometimes called Vaccination or Immunization, like that against smallpox, would not be effective without a well-functioning Immune System.

YOU vs. the BAD GUY: The first process in human defense from infection is for our Immune System to be able to determine “Who am I?” Each of our body cells carries its own identity tag, markers that say: “This cell belongs to Adam” or “This cell is not Eve”. This identification system is known by several names, MHC (major histocompatibility complex) for animals in general and HLA (human leukocyte antigen) for humans specifically. A simple term is “tissue type”.

When a disease causing organism, a pathogen, enters the human body the immune system can identify it as a foreigner because it does not match your personal MHC. The MHC recognizes that the invader is not you; it therefore is an alien “bad guy”. The invading ‘bad guy’ pathogen is then presented to special white blood cells (WBCs) called “T-cells”. The “T” means the WBC was educated in the Thymus, the gland that resides over the Heart. Once the pathogen is recognized the Immune System has several mechanisms for destroying it. It can be eaten by other WBCs, “phagocytized”, and then sent to the Lymph Nodes to be eliminated from the body. It can be destroyed by other WBCs, “Killer T cells” through the release of toxic chemicals. The pathogen can be further identified and destroyed through the Antibody process.

ANTIBODY & VACCINES: The Antibody process is that which was utilized by the historical Smallpox vaccinations or indeed by any type of vaccination program against a Bacteria or Virus. Types of WBCs called “B-cells” because they are educated in the blood, begin the process. When B-cells encounter an invader, a pathogen or protein from a pathogen called an “Antigen”, they digest it. They then ‘present’ it to a T-cell as an identified invader because the pathogen-antigen lacks the correct MHC marker. It is not ‘you’. Your immune system then designs and manufactures a specific Antibody for tagging that invader should it ever appear again in your body. Your Immune System can then ‘remember’ what that invader looks like and readily produce the Antibody to tag it as an invader in the future.

After exposure to a new invader, the Immune System needs about 2 weeks to identify it, tag it and develop a new Antibody. A Vaccine when injected contains a component of the bacteria or virus invader’s proteins to stimulate the beginning of this Antibody production process. There may be some natural inflammation symptoms – some fever, aches – that appear after receipt of the Vaccine while the Immune System is mobilized. After 2 weeks the new Antibody should be ready to protect you.