Monday, November 8, 2010

Your Thymus - The Educator Of Your Immune System

In order to understand our autoimmunity, we must first understand how our immune system works. This is post number two in a series. You can find links to the rest of the series at the end of this blog entry.

Our immune system is our body's defense against harmful invaders. These bacteria, viruses and other foreign bodies and cells hurt our bodies. You can think of your immune system as an internal army waging war against foreign invaders and protecting their home country (our body). They also are designed to protect against our own bodies abnormal cells that have betrayed us, like cancer cells - our own homegrown terrorists. There are generals and soldiers. Generals tell the soldiers what to do and the soldiers act accordingly.

Each person has three types of immunity - innate immunity you're born with, adaptive immunity that develops throughout our lives, and passive immunity which is 'borrowed' from another source.

Adaptive immunity is the slowest to respond because it involves an education of the immune system. The army must 'learn' the difference between good cells and bad cells, and how to act accordingly. Their education has phases that resemble the education you got growing up: Grade school, Jr High and High school, College, and Graduate school.

The education of the adaptive immune system begins in an organ called the Thymus gland. When you were an embryo, special tissue migrated from near your brain, down your neck and into your chest. During this migration, parts of this clump of tissue specialized into other glands (thyroid, parathyroid, etc), broke off and stayed in their current locations.

The thymus gland is now located inside your chest, just below your thyroid gland. If you find the center of the top of your breast bone, underneath this part of your thorax is where it is usually located. The thymus gland is where three groups of immune cells take their grade school through high school education. Because these groups of cells are educated in the thymus, they are called T-cells (T - for thymus).

When you are born, your thymus is large and grows until you are around 2 yrs of age. It takes years to educate the immune system, and when that has been accomplished at puberty, the gland shrinks. It continues to shrink throughout the rest of our lives. It is this shrinking that is thought to be responsible for decreased immunity that the elderly experience.

The job of the thymus (teacher) is to make sure that our army is effective in eliminating foreign cells without hurting our own healthy cells. As the teacher becomes weaker, our army has a greater chance of forgetting how to recognize our own cells. This is why the attacks on our own tissue become stronger when we age - called the aging paradox.

The three groups of cells educated in the thymus are:

* Helper T-cells - help other immune cells do their jobs
* Suppressor T-cells - control the immune system so they don't overreact
* Cytotoxic T-lymphocytes - are taught in the thymus how to recognize markers of self, and markers of invaders (non-self). Their job is to act directly on the bad cells. More than one marker on a cell signifies that it is a cell from the body that has been damaged.

If the teacher is incompetent, the students are not as well prepared to recognize the signals that they should be receiving in their environment to protect the home country (body - self). We must nourish the teacher with an appropriate diet and if needed, supplementation to keep it healthy so it will continue to properly educate its students the T-cells. Still, things can and do go awry, and T-cells can be under-educated or forget how to properly do their jobs. Sometimes there can be too few T-cells to do their jobs properly. All this can be a result of problems within the thymus.

For additional reading:

Part 1: 12 things about your immune system your doctor didn't tell you

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