Jim Harrison, age 12, of Coronado, California, fob his question:
What are antibodies?
"Anti" means "against" and everyone, naturally, lives inside a body. You might suspect, then, that antibodies are our mortal enemies. But nothing could be farther from the truth. In the never ending struggle against assorted germs and infections, they are our dependable allies.
Antibodies, as their name suggests, are against bodies. Their enemies are antigens, and antigens are against the genetic pattern of the cells from which each human body is made. One enemy antigen is the polio virus, so small that 60 million of them could crowd into one human cell. And a row of 2,000 average human cells measures no more than an inch. The soldiers in this war between antibodies and antigens are microscopic, but the numbers in the opposing armies are astronomical.
The human body has built in defenses to protect itself from invading viruses and bacteria, poisons and infections. Its outer protection is the skin that manages to keep out some enemy germs. But some get through and attack the living cells inside. However, they are detected immediately by scouts of the body's defense army. Certain specialized cells detect and tag the invaders as antigens, hostile and destructive to the body's genetic pattern.
Certain lymphoid cells that float in the blood and lymph systems plan the defensive operation. In their own miraculous way, these cells tabulate the structure of a particular enemy. Then they make a suitable pattern to disarm it. Suppose the particular antigen happens to be a boxy midget with a spiked cone. The lymphoid cells design and create a mold with a cone shaped pit to fit over the cone shaped spike. Countless antibodies are copied from this mold and released into the blood stream.
These antibodies seek out and fit themselves neatly onto and into the enemy antigens. Each pair becomes a neutral particle, harmless enough to be devoured by white blood cells. Suppose typhoid germs invade the body for the first time. It takes about IO days to design a tailor made weapon and build an army of antibodies. Meantime the enemy antigens rampage unchecked. Then the defending army takes the field and the disease begins to subside. When the battle is won, a few antibodies may remain floating in the blood stream. In any case, the lymphoid cells never lose the design for this particular weapon. If typhoid germs attack a second time, the antibodies are produced to oppose the invasion.
During a lifetime, the body creates perhaps 100,000 tailor made antibodies, each designed to neutralize and disarm a special antigen. All of these designs are on file, ready to go into fast production. Diseases such as measles strike only once in a lifetime. If measles germs attack a second time, the right weapon is on hand to stop them. This protection learned from experience is called immunity. After one attack, the body is immune to measles. Your blood stream carries sample antibodies to cope with a large assortment of. enemy antigens.
Doctors are learning how to improve the body's immunity defenses. The right antibodies are produced when the enemy attack is very mild and often when the germs are already dead and harmless. We get vaccinated with the right serum to prod the body into creating samples of the right antibodies to protect us from smallpox. We now have vaccine serums to make us immune from enemies such as measles and polio. Meantime researchers in preventive medicine are busy seeking vaccines to whip other antigens before they start attacking.