Educational recap: What is the immune system?

Based on the Patient Education class from February 15, 2014, here are some notes to keep your memory fresh and your family and friends informed.

What is the immune system?

The primary function of the immune system is to protect, prevent and limit infection.

Think of your immune system like a military operation. An army inside your body consisting of cells, tissues and organs designed to defend against invading microscopic "beasts." Organisms like bacteria, parasites and fungi that can wreak havoc in your body. Viruses also cause infections, but are too primitive to be considered living organisms. It is the immune system's job to defend against or destroy them.

Where is the immune system?

All immune cells come from the bone marrow.

Bone marrow

Your bone marrow contains the stem cells that are the precursor to innate immune cells that are first responders to fight infection.

These cells become what is know as B, T, and NK cells. B and T cells (adaptive immune cells) are responsible for fighting invaders based on previous bouts with a particular microbe or microbes (known as immunological memory).

NK cells (Natural Killer) respond immediately to infection and have the ability to be retained like memory adaptive cells. These cells are also known as lymphocytes.

Skin

The skin is the first line of defense against infection. Some skin cells have the ability to secrete antimicrobial proteins, and immune cells can be found in certain layers of the skin.

Bloodstream

Immune cells are on constant patrol through your bloodstream. White blood cells are immune cells. When a blood test is done your "white cell count" is a measure of what's going on with the immune system.

Thymus

This is where T cells mature. This small organ is located in the upper chest behind the sternum.

Lymphatic system

Any effective army needs a good communications network. The immune system is no different. Millions of cells, organized in sets and subsets swarm together to pass information back and forth in response to an infection. Once the alarm is raised, they go into action producing chemicals. These chemicals allow the cells to control how they respond, recruit other immune cells, and confront the invasion.

The lymphatic system is a complex series of tissues and vessels composed of extra cellular fluid and lymph nodes. The lymphatic system is a conduit for travel and communication between tissues and the bloodstream. Immune cells travel through the lymphatic system and converge in lymph nodes.

Lymph nodes are the hubs where immune cells sample information brought in by the body. For example, if adaptive immune cells in the lymph nodes recognize a piece of dangerous microbe from a distant area, they sound the alarm and activate the troops to attack that pathogen.

The immune system is very complex. It can recognize and remember millions of different enemies, and it can produce the correct secretions to wipe out nearly all of them.

Spleen

The spleen is not directly connected to the lymphatic system, it is important for gathering information from the blood stream. Immune cells are hanging out in specific areas of the spleen and react accordingly to any blood-borne pathogens.

Mucosal tissue

Specialized immune centers are located in mucosal tissues like the respiratory tract and the gut. For instance, there are special areas in the small intestines wherein immune cells can access samples from the intestinal tract.

Accidents happen

Like our military, sometimes the immune system hits the wrong target. When that happens, the results are allergic reactions, arthritis and a form of diabetes. If the damage is extensive, other kinds of diseases result.

Summation

Scientists continue to study how the body defends against and destroys invading microbes, infected cells and tumors while ignoring healthy cells. The study of how genetics play a role in the human immune response is in the mix as well. Hopefully, with the onset of new technologies advancing genetic research, we will learn even more how the body protects itself from disease.

Here's to your healthy immune system!

Chuck.