Frank Hawker, age 10, of Coeur d' Alene, Idaho, for his question:
WHAT IS THE RH FACTOR?
Rh factor is a substance in the red blood cells of most people. Red blood cells that contain the Rh factor agglutinate or clump if they come into contact with an antibody called anti Rh. This reaction can produce serious illness or even death.
Persons who have the Rh factor are known as Rh positive. Those lacking it are called Rh negative.
Karl Landsteiner and Alexander Wiener, who discovered the factor in rhesus monkeys in 1940, named it Rh for the monkey.
Anti Rh doesn't occur naturally in the blood. But if an Rh negative person receives a transfusion of Rh positive blood, anti Rh may build up in his blood plasma. By the time the antibody has been produced, the donor blood is, in most cases, so diluted that no serious reactions take place.
But if the patient receives later transfusions of Rh positive blood, the anti Rh will attack the Rh positive red blood cells and cause agglutination.
The Rh factor is inherited. The child of an Rh negative mother and an Rh positve father may be Rh postive. Before birth, some of the body's blood cells may enter the mother's blood. Then the mother may build up anti Rh.
Most of the antibody does not form until after the baby is born, however, so it seldom causes any problems with the first child. But if the mother becomes pregnant with another Rh positve baby, she now has a ready made supply of anti Rh. The flow of large amounts of her anti Rh into the child's blood can cause clumpting and destruction of the infant's red blood cells.
When Rh disease does occur, doctors treat the condition by immediately replacing the baby's blood with fresh blood. In most cases, this procedure eliminates any long term effects of the disease.
Rh disease can result in severe anemia, brain damage and even death. Such severe reactions take place in only about one of 20 cases in which the woman is Rh negative and the man is Rh positive.
Even among these couples, doctors can usually prevent RH disease today by injecting the mother with a serum shortly after she gives birth to an Rh postive child. The serum contains anti Rh, which destroys any of the baby's cells in her blood before her body has time to produce its own anti Rh.
Karl Landsteiner, who along with Alexander Weiner discovered the Rh blood factor, earlier discovered the main types of human blood: A, B, AB and O. He won a 1930 Nobel prize for this important discovery.
Landsteiner also contributed information on how the body becomes immune to certain disease bacteria. In addition he proved that a virus causes poliomyelitis.