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Sight of sickness fires up immune response, study suggests

April 27, 2010 | 12:08 pm

Next time you glare at someone for sneezing near you in an elevator, be sure to look long and hard at the offending germ-spreader: it may protect you from getting what he or she has.

A new study published this month in Psychological Science suggests that the very sight of sickness prompts the immune system to mount defenses against illness. That finding follows naturally from earlier research suggesting that disgust -- the typical first reaction we have to a person with, say, open sores -- may be part of a "behavioral immune system." Revulsion, after all, makes us more likely to move away from the source of infection -- and thereby less likely to catch it.

But this is the first experiment that demonstrates a direct link between viewing signs of illness and heightened immune response in response. In it, University of British Columbia psychology researchers took 19 women and nine men and, after testing their blood for a very common marker of immune response called interleukin-6, or IL-6, divided them into two groups. Each group was first shown a 10-minute slideshow of something bland -- furniture. In a second session, one group watched a 10-minute fright fest of disease symptoms, including sneezing, oozing sores and pox. The other group saw a slideshow of gun-toting people, many aiming their weapons directly at the viewer. 

For subjects who had watched the disease fright fest, their levels of IL-6 rose almost 25% higher than their pre-slideshow levels -- an immune response significantly more robust than that among subjects who had watched the gun-slingers. Neither group responded to the neutral, bland slideshow with a rise in IL-6.

There's obviously a limit to how often and how high you can gin up these defenses against disease. After all, if you could sustain the heightened IL-6 response to seeing sick people, doctors and nurses would be veritable titans of immunity. And, of course, we may all waste an occasional immune response on someone else's condition that's not even contagious. But the authors note that our reaction to sickness is "presumably adaptive in origin."

Oh, and if you're going to stare (which isn't polite), at least say "gesundheit!"

-- Melissa Healy