When a physician or a nurse injects a few drops of measles vaccine into a child, the particles in that liquid set off an incredible chain of events within the child’s body. At the end of that sequence, the child is immune to any live, disease-causing measles virus.
The vaccine triggers the child’s immune system. And what a marvel that system is. Millions of microscopic blood cells, each smaller than a dust particle, swing into action. They create chemicals designed specifically to knock out the measles virus. They marshal the aid of scavenger cells to chew up the attackers.
Scientists have learned how immunity works and how it fights invading bacteria, viruses, parasites, and pieces of these called antigens. Or how it sometimes turns against the body itself, causing diseases like arthritis, rheumatic fever, perhaps even diabetes. Or how it safeguards you from cancer.
Measles, influenza, and polio no longer kill much of the world, thanks to vaccines. New medications and treatments are coming from research in medicine, chemistry, and genetic engineering.
Scientists today feel overwhelmingly that they have passed the threshold of major discoveries. The way is open to find the causes of cancer and a dozen other diseases, how to treat them, and possibly how to prevent them.
“We are dealing with an unparalleled explosion of information on cancer biology,” says Dr. Steven Rosenberg, chief of the surgery branch of the National Cancer Institute.
Sara Brooks, 4, of Sacramento, California, owes her life to this new knowledge. She inherited a defective immune system and had no protection against invading germs from the day she was born. Doctors kept Sara alive for 5 months in a little three-sided box with air filters. Her parents, Steve and Sheryl Brooks, could not touch or cuddle her. A single stray germ could have killed her.
“Sara was pretty sick for a while,” says her mother, “but now the doctors consider her cured. We call her a miracle baby.”
Dr. Morton J. Cowan of the University of California at San Francisco gave Sara a defect-free immune system by transplanting bone marrow from her father into her body. His healthy bone marrow contained all the cells Sara needed.
Bone marrow transplantation also has been successful in fighting leukemia. It replaces the diseased immune system by producing healthy red cells and platelets and the immune system’s white cells. This transplanting occurs after the leukemia is blasted with X rays and chemicals that destroy both the cancer and the patient’s bone marrow.
In this same way, bone marrow transplants have helped several workers who received deadly doses of radiation at the nuclear accident at Chernobyl in the Soviet Union. The radiation had destroyed their immune systems.
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