The past five years have brought a flood of discoveries about the body's capacity to prevent infection. Scientists have finally solved the mystery of how the body creates both antibodies and immune

BODY AT WAR

The past five years have brought a flood of discoveries about the body's capacity to prevent infection. Scientists have finally solved the mystery of how the body creates both antibodies and immune cells, the two agents of the immune response that together are capable of recognizing every toxin, bac­terium and virus that exist in nature. They know more, too, about the genes that predisposejhe child to immune diseases, and for the first time, they are pinpointing the links between the brain and the immune system.

The breakthroughs offer hope for a host of diseases, from allergies to multiple sclerosis, as researchers develop treatments that act on the im­mune system. Two vaccines against melanoma, a deadly form of skin cancer, are being tested. Potent hormones of the immune system, called cytokines, are being used experimentally to heal wounds and to boost the body’s de­fense against cancer. Clinical trials are under way to test nine AIDS vac­cines, something many researchers considered pie in the sky five years ago. The immune system is one of nature’s most remarkable creations, a complex network of billions and billions of highly specialized cells as well as the stag­gering array of potent hormones. Cracking its secrets has proved a far more difficult task even than splitting the atom.

The foundation of today’s advances dates back to the late 1800s, shortly after Louis Pasteur proved his theory that germs cause disease. European researchers identified antibodies in the blood that appeared to attack and defeat bacteria that had managed to invade the bloodstream. The scientists also observed much larger cells that acted as wandering garbage collectors, gobbling up loose material of all sorts in the blood, from viruses and bacteria to loose bits of the body’s own cells. For years, researchers argued over whether it was these cells, called macrophages, or the antibodies, or both, that kept the body free of invaders.

Antibodies and macrophages, it turns out, represent only two of the many soldiers that keep germs away. Over the next decades, researchers discovered a half-dozen other major classes of immune cells coursing through the blood. Most important are the T-cells, so named because they mature in the thymus, a pale-gray gland that sits behind the breastbone. For every species of virus, from smallpox to the common cold, and for every species of bacteria, there are a T-cell and an antibody that recognize it as foreign and as a target for attack. Even more remark­able, scientists have found, T-cells and antibodies have a mysterious capacity to recognize and destroy chemicals created in the laboratory, substances the body has never encountered in its millions of years of evolution. Every time an organic chemist makes a new chemical, the immune system already has a cell for it.

IMMUNE WARRIORS

Virus
Macrophage
Helper T-cell
Killer T-cell
Antibody
B-cell	m-.
Major histocompatibility complex molecule (MHC)
Antigen

Дата добавления: 2015-11-04