Observing disease symptoms causes a more vigorous immune response

We know that social status, positive versus negative affect, etc. can influence immune system robustness. Now Schaller et al. show that the mere observation of photographs depicting symptoms of infectious disease can boost the subsequent elevation of proinflammatory cytokines released by white blood cells in response to a bacterial stimulus. The effect was specific to the perception of disease-connoting social cues; it did not occur in response to a different category of stress-inducing interpersonal threat. The abstract and a few clips:

An experiment (N = 28) tested the hypothesis that the mere visual perception of disease-connoting cues promotes a more aggressive immune response. Participants were exposed either to photographs depicting symptoms of infectious disease or to photographs depicting guns. After incubation with a model bacterial stimulus, participants’ white blood cells produced higher levels of the proinflammatory cytokine interleukin-6 (IL-6) in the infectious-disease condition, compared with the control (guns) condition. These results provide the first empirical evidence that visual perception of other people’s symptoms may cause the immune system to respond more aggressively to infection.

This linkage may have been adaptive in ancestral ecologies, as individuals characterized by perception-facilitated immune responses would have had reduced likelihood of succumbing to pathogenic infections...People are sensitive to visual stimuli connoting the potential presence of infectious pathogens in others. These stimuli include anomalous morphological and behavioral characteristics (e.g., skin discolorations, sneezing) that suggest infection with disease-causing microorganisms. When perceived, these stimuli trigger psychological responses—such as disgust and the activation of aversive cognitions into working memory—that inhibit interpersonal contact.