How does the immune system really work?

  • Ayda Ersoy - The Diet Doc

Do you often get colds or experience fatigue, muscle aches, sinus infections and digestion difficulties?

Immune problems have all been linked to inappropriate nutrition — which is different for each of us, because we are each individually unique, both genetically as well as in the environmental context of our lives.

Immune is derived from the latin word immunis, which means free or untouched and essential for survival. Our immune system is amazingly complex. It is what helps our body maintain homeostasis, particularly in the intestine, as the largest organ of immunity in the body.

A healthy immune system has the remarkable ability to distinguish between the body’s own cells and foreign cells, thereby allowing it to identify and fight infections and anything that is foreign to the body.

This is all the more remarkable when you remember that more than 99 percent of the human microbiome is “good bacteria” that regulates our digestion, metabolism, and immunity.

The most important and powerful system in the body’s defense mechanism is the lymphatic system. This is responsible for cleansing the cellular environment, returning proteins and tissue fluids to the blood, providing a pathway for the absorption of fats and fat-soluble vitamins into the bloodstream and, most importantly, defending the body against disease.

The lymphatic system works together with many different organs and systems to keep us alive and healthy. The world around us contains countless viruses, bacteria, fungi and parasites capable of surviving and thriving inside our body. Collectively, we call these pathogens, and they are responsible for many diseases. The lymphatic system helps our bodies deal with pathogens.

The lymphatic system — with its tissues and organs that produce, store, and carry white blood cells that fight infections and other diseases — includes the bone marrow, spleen, thymus, lymph nodes, and lymphatic vessels.

Our body has many different types of T cells (Thymus-dependent cells), and all of them are important to the immune system. T helper cells regulate the immune system and activate other white blood cells. Cytotoxic T cells destroy virally infected and cancerous cells.

Memory T cells keep a record of every infection you have been exposed to, so if you are exposed to the same infection again your immune system can recognize that you are under attack very quickly and respond.

About 80 percent of circulating lymphocytes are classified as T cells. B cells (bone marrow derived cells) comprise around 10-15 percent of circulating lymphocytes, and NK (natural killer cells) around 5-10 percent. These are specialized attack cells that recognize certain infections that the T cells might overlook.

The Thymus is where T cells mature, and therefore plays an important role in the immune system. It gradually decreases in size and capability as we age, making elderly individuals especially susceptible to disease. When a person suffers from autoimmune disease, it means that their suppressor cells are not working properly.

Homeostasis is the process in which the body maintains normal, healthy ranges for things like temperature, energy intake and growth.

The immune response plays an important role in maintaining homeostasis by preparing the body to fight off infection, and to help the healing process.

During infection, the immune system will cause the body to develop a fever and an increase in blood flow to bring oxygen and other immune cells to where the infection is. It also helps in wound healing, to reform the correct barriers in organs so that they can correctly participate in homeostasis.

Why am I telling you all this detailed information?

Because the immune system is our body’s natural defense mechanism. We are capable of fighting any disease with our powerful, natural immune defenses.

Simple conditions like colds and influenza are caused by viruses that a healthy immune system can defend itself against.

So before thinking of getting a flu shot, or taking lots of antibiotic, make sure that you first ask yourself: am I taking care of my body well, and what do I need to change to improve my health and my body’s natural defense?

In my next article I will explain what is the best defense against disease.


Ayda Ersoy is a nutrition and fitness director at The Diet Doc Hawaii. She can be reached at, or (808) 276-6892


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