T Cells, Hematogenic Cells - The Players In The Immune System : Part 4

UltraLongevity: The Seven-Step Program for a Younger, Healthier You
By Mark Liponis, M.D.

(Page 4 of 5)

T Cells

The other major group of lymphocytes is the T cells (T stands for thymus, the body organ in which they mature).

T cells look like B cells under a microscope-they are spherical, with a big nucleus and not much cytoplasm (the stuff that surrounds the nucleus). These T cells are the marines of your homeland security team. Just as every marine has a job classification, or a military occupational specialty (MOS), every T cell also has an MOS.

The T cells are divided into occupations such as helper T cells, suppressor T cells, and cytotoxic T cells. These are all very specialized functions, analogous to real marines assigned to the bomb squad, the recon team, and so forth. Some T cells (cytotoxic, or CD8, cells) attack invaders and infected cells directly, while others (helper, or CD4, cells and suppressor T cells) help regulate the immune response and keep it from becoming overactive. Cytotoxic (or cell-killing) T cells identify foreign organisms inside our cells and destroy those infected cells by recognizing changes in their surface proteins. They work in concert with the suppressor and helper T cells, which regulate the activity of the cytotoxic T cells.

Suppressor T cells help to regulate the immune reaction by preventing cytotoxic T cells from killing healthy cells. Helper, or CD4, T cells help cytotoxic cells kill infected cells. You may have heard of CD4 cells in the context of HIV infection, because these are the cells targeted by HIV (the human immunodeficiency virus). Low levels of CD4 cells signal a serious HIV infection.

Also important are specialized cells known as natural killer cells (NKs), which are assassins trained to destroy damaged, cancerous, or infected cells in the body. NK cells are similar to cytotoxic T cells but are more powerful.

Let's say you are exposed to a virus. One of the reasons viruses are so dangerous is that they don't just cruise around the tissue or blood and hide there, waiting for your body to destroy them. They actually creep inside your cells, and that means your body has to destroy some of its own cells if they become infected.

Once inside your cells, a virus messes with your DNA, tricking your cells into reproducing the virus by mingling its own DNA with yours. Then the virus uses your cells' DNA-processing system to replicate its own DNA too.

When a cell becomes infected with a virus in this way, the situation starts to resemble the scene from the science-fiction movie Alien in which the aliens, growing inside the characters' bodies, burst out, killing them.

Unfortunately, the only way to prevent the dangerous alien that is a virus from reproducing is to kill the newly infected cell. That's where the killer T cells come in. Natural killer cells sense a distress signal from the cells infected by a virus. The call may come from any type of cell-one that lines the nose or throat, or that resides in your intestines or in your skin.

When NK cells detect an infected cell, they use a special weapon to destroy it-a kind of plug that's injected into the cell membrane (the outside boundary of the cell). The plug, which has a small hole in it, is a protein called perforin. The NK cell then injects a substance called granzyme (or, more formally, exogenous serine protease) through the plug, which destroys the cell like a bomb.

That's how the natural killer cells work to destroy cells infected with viruses. Other parts of the immune system attack viruses directly, but natural killer T cells are those responsible for killing viral-infected cells, including the ones carrying HIV, which is why it's important to have a high count of NK cells in your blood.

Natural killer cells are involved in many search-and-destroy missions for our immune system. They're also important in killing cancerous cells that crop up in our bodies, ideally before they can grow into tumors. Cancer in the human body is not as rare as most people think; cancer cells are actually quite common. But for a number of reasons, most of these cells are never allowed to grow into tumors capable of killing us. One of the reasons for this is that the assassin-like NK cell snuffs them out before they have a chance to replicate.

Several therapies have been shown to increase NK activity, such as guided imagery, qigong, special breathing techniques, ginseng, and certain Chinese herbs.

Hematogenic Cells

Besides lymphocytes and macrophages, the third line of immune cells includes the blood-forming, or hematogenic, cells. Hematogenic cells are the cells from which our red blood cells, and many white blood cells, are produced. During a routine physical exam, your doctor probably performed a blood count, measuring the number and types of white blood cells seen in a drop of your blood. A high number (or high concentration) of white blood cells is usually a sign of some infection or stress on the body.

Many types of white blood cells are visible in a drop of blood. About half of them are known as neutrophils, aka polymorphonuclear cells, or polys for short.

I like calling these cells PMs, because that also stands for Pac- Man, the video game whose little creatures resemble PMs. Like Pac-Men, PMs sense invaders, chase after them, and once they've caught their quarry, they literally gobble them up.

Some of the other white blood cells include eosinophils, basophils, and monocytes. Each of these cells has its own specialized function. Eosinophils, for example, play a role in allergic reactions, as well as disorders like asthma. They are also involved in fighting off parasitic infestations.

As you know now, our immune system contains many specialized fighters possessing specialized weapons to deal with varied and sometimes uncommon threats. The ones mentioned above are just a few of the soldiers who are constantly fighting to keep your personal homeland safe. Right now, inside your body, they are all at work.

© 2007 by Mark Liponis, MD

About the Author

Mark Liponis, MD, is the medical director of the Canyon Ranch Spa in all its locations. He is the coauthor of New York Times bestseller UltraPrevention, which won the 2003 Books for a Better Life Award in the health category.