Every minute of every day wars rage within our bodies. The combatants are too tiny to see. Some, like the infamous virus that causes AIDS, are so small that 230 million would fit on the period at the end of this sentence. Of all the body’s enemies, the virus is both the simplest and the most devious of all. A virus, such as the Human Parvo Virus B19, contains instructions for making copies of itself. When a virus enters one of our cells it issues its own instructions. The cell becomes a virus factory, producing identical viruses. Eventually they may rupture the cell, killing it. Viral clones fan out to invade nearby cells.
About one trillion strong, our white blood cells constitute a highly specialized army of defenders. The phagocytes, which are soldiers in this army, are the first to attack viruses. When they come upon a cell that has burst, they eat up the wreckage and in the process consume the viruses. But they aren’t able to destroy these foes enough to keep them from infecting nearby cells.
The T cells are a more sophisticated part of our immune system. They are trained to recognize invaders. They then send urgent chemical signals to killer T cells. The message is to multiply quickly. The killer T cells puncture the cell membranes bacteria or destroy infected cells before viruses have time to multiply.
During stress the body releases large amounts of a steroid called cortisol. When our soldiers the macrophage recognize and encounter cortisol they can no longer respond to infection.
Exercise may enhance the immune system. It stimulates the brain to release chemicals called endorphin and enkephalin. They also seem to reduce anxiety and cause a sense of well being.
Even more startling, some studies suggest that they affect macrophage and T cells. Exercise may also result in increased levels of interleukin-1 and interferon, both of which strengthens our defenses.
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