Infection can activate two dramatically different responses
The difference between staying well and suffering days of misery depends on which of two contradictory ways the immune system reacts to infection by the flu. One strong reaction releases inflammatory chemicals leading to sickness, researchers report online August 25 in PLoS Genetics. An equally strong but opposite reaction produces anti-inflammatory compounds and fights off the flu without producing symptoms.
Most of what researchers know about influenza’s effect on people comes from studies of people who are already sick. But Alfred Hero and his colleagues wanted to know how some people seem to be able to avoid getting sick. The researchers infected 17 volunteers with a strain of seasonal flu called H3N2/Wisconsin.
Nine of the volunteers got sick. Some of the others reported feeling under the weather, but had no clinically discernible symptoms. The researchers drew blood before the flu inoculation and every eight hours for five days after the