Humans have a natural aversion to those who are ill. When we see others who seem under the weather, we experience a powerful emotional response—disgust—and do our best to avoid those who might be contagious. Now a study shows that seeing sick people can even prompt changes in the immune system.

Researchers at the University of British Columbia showed subjects one of two different slide shows—either a depiction of people brandishing guns or images of individuals who were obviously ailing. Immediately after the subjects viewed the slide shows, researchers drew their blood, exposed each sample to bacteria and then measured the levels of a substance known as interleukin-6 (IL-6), which is secreted by white blood cells as a response to stress or trauma. Although the subjects rated the gun photographs as being more stressful than the illness images, the blood work told a different story. Whereas the gun images prompted a mere 7 percent increase in IL-6, levels of the substance were elevated 24 percent after viewing pictures of sick people.

“It makes evolutionary sense that the immune system would respond aggressively only when it’s really needed,” says Mark Schaller, a psychologist and co-author of the study. “If I see a bunch of sick people, maybe a big infection is around, and I better kick my immune system into high gear.” It is unclear exactly how an image gets trans­lated into a mustering of immune cells, Schaller says, but many neurochemicals connect the brain to the immune system—more studies are needed to tease out the exact chain of events.

This article was originally published with the title Natural Immunity.

3 Comments

1. 1. jtdwyer 10:29 PM 10/3/10

   Since the Interleukin-6 is produced by T-cells in the blood, the conditions contributing to the increased Il-6 production in response to bacterial exposure must have occurred prior to the blood being drawn (presuming that showing the pictures only to the blood samples makes no difference) and have been present in the blood sample.
   
   There was no mention of any variation of contributing factors, such as an increased number of T-cells or other blood agents, but there must be something else different about the blood that would point to the initial response source.
   
   That being said, there's not likely any real benefit in tricking the immune system: there is almost certainly a cost to the immune system response preparation.
   
   It might also be interesting to perform the same experiment on hospital staff, presuming the were not included in the prior test subject population...

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2. 2. Laertes 09:24 AM 10/5/10

   It is interesting that the brain may stimulate an immune response, probably from the pituitary or the glia cells directly. As for jtdwyer's suggestion, I would bet that hospital staff has a lower IL-6 response. The body tends to become acclimated to stimuli. Constant exposure to sick people might lessen IL-6 response over time. What would be interesting would be the hospital staff's ability to fight off infection once acquired. Would a lower IL-6 response (if confirmed)affect their ability to recover from an infection?

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3. 3. domfischer 01:49 PM 10/6/10

   Ergo... nurses and physicians should never be sick. Hum!

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