Immune Systems Increasingly On Attack

"We believe it's about half and half," Cookson said. "You need environmental factors and you need genetic susceptibility as well."

Some researchers have begun to try to identify specific genes that may be involved, as well as specific components of bacteria or other pathogens that might be used to train immune systems to respond appropriately.

"If we could mimic what is happening in these farm environments, we could protect children and prevent asthma, allergies and other diseases," von Mutius said.

Some researchers are trying to help people who are at risk for allergies or already ill with autoimmune diseases.

With new research suggesting that food allergies may be occurring earlier in life and lasting longer, several small studies have been done or are underway in which children at risk for milk, egg and peanut allergies are given increasing amounts of those foods, beginning with tiny doses, to try to train the immune system.

"I'm very encouraged," said Wesley Burks, a professor of pediatrics at Duke who has done some of the studies. "I'm hopeful that in five years, there may be some type of therapy from this."

Another promising line of research involves giving patients microscopic parasitic worms to try to tamp down the immune system.

"We've seen rather dramatic improvements in patients' conditions," said Summers of the University of Iowa, who has treated more than 100 people with Crohn's disease or ulcerative colitis by giving them parasitic worms that infect pigs but are harmless to humans. "We're not claiming that this is a cure, but we saw a very dramatic improvement. Some patients went into complete remission."

Doctors in Argentina reported last year that MS patients who had intestinal parasites fared better than those who did not, and researchers at the University of Wisconsin are planning to launch another study as early as next month testing pig worms in 20 patients with the disease.

"We hope to show whether this treatment has promise and is worth exploring further in a larger study," said John O. Fleming, a professor of neurology who is leading the effort.