The Immune System –Lesson 101

By Sheila Kun RN, BSN, MS, CPN, FCCP

With the COVID 19 epidemics, there has been tremendous interest in understanding the virus and how our immune system work. Our CDC has extensive, detailed information on the Corona virus. But for those with a positive testing, the response to the invasion of this virus varies. At this point, there is no specific answer to the question raised. However, the word of “how your immune system works with the exposure” has been stipulated that accounts for the degree of how severe your case is. I thought it is important to understand how our immune system work before embarking into seeking out answers on such complex processes. If you open up one of the health science books from your high school era, you will be amazed by how well it presents the immune system. But for those who might not have access to this basic science book, let me summarize the immune system for you. I call this “The immune system 101”.

Your body’s last and most sophisticated line of defense against pathogens (organisms that cause diseases) is your immune system. The cells in the immune system are “tailor-made” for each pathogen. As a result, the immune system can recognize, seek out, and destroy specific pathogens throughout your body.

Pathogens that enter your body for the first time often cause disease. You might ask, why can’t my immune system fight against this pathogen? Well, your immune system works this way: your immune system must recognize a new pathogen first; then it takes time to build up its weapon to fight against the pathogen. So the next time around, if the same pathogen enters your body, the immune system says: “I have known you before, and I have built up a weapon to fight against you.”

Much of your immune system is contained within your lymphatic system. Your lymphatic system is a network of vessels that collects fluid from the tissues of your body and returns it to the blood-stream. The fluid that flows through the lymphatic system is called lymph. The lymphatic vessels have hundreds of small stations, called lymph nodes. Each lymph node acts as a sort of filter. Phagocytes (white blood cells that “eat up” foreign cells) and cells called lymphocytes are present in the lymph nodes and attack pathogens as they pass through.

 Lymphocytes are white blood cells – B cells and T cells in your immune system.  B cells produce substances called antibodies. Antibodies are proteins that attach to the surface of pathogens. This binding action keeps the pathogen from harming the body. It also helps phagocytes find and consume the pathogen.

Like B cells, T lymphocytes (T cells), live in the blood and lymphatic system of your body. T cells are killer cells, they kill pathogens directly. Other T cells can be helpers or suppressors; they don’t produce antibodies, but they produce substances that regulate the activities of other cells of the immune system.

One of the regulatory substances that T cells produce is called interferon. Interferon stimulates phagocytes and other cells, including B cells, to fight off infection. When an infection has been brought under control, some of the T cells then “turn off” the activated cells with other chemicals. T cells also help your immune system “remember “pathogens in case they ever reenter your body. This memory capacity, of T cells, along with memory capacity of B cells, is what maintains the immunity of your body to pathogens.


Your homework assignment from the Care Ministry this week: Name the main functions of the B and T cells.

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