The Players In The Immune System : Part 5

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

(Page 5 of 5)

Border Security and the Alts

As discussed, one of the major duties of our body's homeland security system is border security, and it's a big border, including all of the surfaces that come into contact with the outside world. Invaders are constantly appearing, with the intent of not just looking around, but of doing us harm. Therefore, we need more than just a few cells of our immune system patrolling these borders.

This is where the so-called ALTs, or associated lymphoid tissues, enter the picture. ALTs are large clusters of immune cells located at fairly regular distances along our borders. For example, in the gut we have GALT (the gut-associated lymphoid tissue), which resembles thousands of strongholds positioned throughout the gut's lining, protecting the border between us and what's inside our gut.

The gut is an especially important border, not only because of its size (approximately the area of a tennis court when fully flattened), but also because of the constant barrage of bacteria and other microbes trying to break through it. The only barrier is a thin membrane a single cell thick.

Such a big assignment requires a large force, which is why the GALT alone accounts for about half of all the cells in our immune system. Most of these cells are T cells, but B cells, as well as macrophages, are also stationed in the GALT.

However, the borders of our homeland extend beyond the gut. There's also our skin, and the mucous membranes that line our nose, mouth, sinuses, throat, and lungs. Each of these boundaries needs its own defense force, so like the gut's GALT, we also have a SALT, a NALT, a TALT, and a BALT, whose acronyms stand for the skin-, nose-, throat- (or tonsils), and bronchial-associated lymphoid tissue. These aggregations of lymphoid tissue represent more than 70 percent of our immune system.

The Complement System

We've already seen a number of ways our immune system's cells can fight off threats. For example, an MP (macrophage) or a PM (poly) can gobble up a germ, or an NK (natural killer) can inject a granzyme grenade into an infected cell.

There are several additional ways the immune system kills off bodily threats, using more sophisticated tools that allow it to rid the body of more than one invader at a time. After all, if faced with an invasion by billions of enemies, hand-to-hand combat alone won't work.

One of these tools is a chemical weapon known as an antibody, which is produced by the B cells. Yet another process occurs when the antibody nabs its target. The same handle, or tail, that signals to the immune system that it's caught something also triggers the deployment of a system of chemical weapons known as the complement system.

The complement system is an exceedingly convoluted system of chemical warfare. In simple terms, think of the complement as something akin to an arsenal of nuclear weapons. The complement system is always present in our body, but its different components, of which there are at least thirty, are generally disassembled.

These complement components are produced mainly in the liver, but also by macrophages and other cells of the immune system. Separately, each of the complement components is harmless. But if the entire array is assembled, watch out! A nuclear reaction will take place.

The trigger for the complement construction transpires when those antibody pitchforks skewer so much prey it becomes clear additional help is needed. That critical level of battle initiates the assembly, or activation, of the complement system.

Activation of the complement system is one of the body's most impressive functions. Luckily, it is triggered only by severe issues, such as pneumococcal pneumonia or meningitis. It also occurs in organ transplantation-normally our immune system produces such a vigorous reaction to a transplanted organ that it causes organ rejection, which is why drugs must be given to suppress complement activation.

As in a nuclear reaction, once the complement system is activated, a process of events is triggered that is hard to stop and usually results in the death of the invaders.

That destruction takes the form of leaking capillaries, swelling, accumulation of lymph fluid, and the release of distress signals that attract even more fighters from all over the body, as well as the release of pyrogens (chemicals that raise body temperature, causing a fever) and general deployment of all available weapons, including nitric oxide and free radicals.

This entire process makes you feel very sick. If it continues, due to an overwhelming threat, it can lead to shock, organ failure, and death. Complement activation is therefore generally reserved for only the most serious circumstances.

The Communications System

The final part of the homeland security detail you need to appreciate is the communications link.

For a battle in the outside world to go well, good communications are required: satellites, cell phones, radios, and microwave systems all communicate strategies as well as locate the enemy so it can be outflanked.

Your body has a similar kind of communications system.

The main category of communications devices is composed of the cytokines, of which more than one hundred have been discovered. Cytokines are proteins-such as interleukins, interferons, TNFs (tumor necrosis factors), pyrogens, and shock proteins-that send signals through your body to distant parts of the immune system.

Let's say you develop an ingrown toenail. First the Pac-Men engage with the enemy in the toe. But if they discover, say, an infection too powerful for them to fight on their own, they send out a message through the bloodstream that acts as both a distress and a homing signal, calling for reinforcements to the toe. This signal goes out in the form of cytokines.

Cytokines tell the rest of the immune cells where to go, and they follow the cytokines' scent just as a bloodhound sniffs out a trail, leading them right to the toe where the infection is wreaking havoc.

Drug companies are constantly researching cytokines and how to turn them on or off to treat different conditions. Cytokines are used to treat some infectious diseases, such as hepatitis, which is caused by a virus. For example, people are given interferon treatments if they are infected with hepatitis C. In autoimmune diseases such as rheumatoid arthritis or colitis, cytokine blockers including Enbrel, Humira, and Remicade are used to block the effects of the cytokines activating the immune system.

The immune system is so complicated that it would take volumes to explain all its details. But this brief introduction should provide you with a basic understanding. Knowing how your immune system operates can save your life-the more you know about it, the better you will treat it, and, in return, the better it will treat you.

© 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.