Yale Scientists Uncover How the Immune System Can Alter Our Behavior

Researchers at Yale Illuminate the Role of Immune System in Modifying Behavior

Recent studies have unveiled the critical function of the immune system in shaping behavioral responses. This role is executed through the immune system’s capacity for recognition, which subsequently triggers defensive behaviors against harmful substances, as communicated from antibodies to the neural system. In experiments involving mice, it was demonstrated that blocking IgE antibodies—which are instrumental in activating mast cells that convey signals of aversion to the brain—resulted in the mice no longer evading allergens. This emphasizes the significance of the immune system in enabling animals to sidestep environmental risks.

The mere aroma of shellfish can intensely affect those who are allergic, thereby making them more prone to steer clear of it. Similarly, people who have suffered from foodborne illnesses resulting from a particular food item are likely to refrain from consuming it in the future.

For an extended period, the scientific community has recognized that the immune system is instrumental in our physiological responses to environmental allergens and pathogens. However, its role in influencing behavioral reactions to allergenic stimuli had remained ambiguous.

In a scholarly article recently published in the journal Nature, led by Yale researchers, it has been confirmed that the immune system is pivotal in modifying our behavioral patterns.

“Immune recognition governs behavior, particularly defensive reactions against harmful substances, which are initially relayed by antibodies and subsequently processed by our brains,” stated Ruslan Medzhitov, Sterling Professor of Immunobiology at Yale School of Medicine, investigator for the Howard Hughes Medical Institute, and the senior author of this research.

The study indicated that absent the communication facilitated by the immune system, the brain refrains from alerting the organism about impending environmental hazards, thereby forgoing any avoidance of such risks.

The research team, operating in Medzhitov’s laboratory, was spearheaded by Esther Florsheim, who was a postdoctoral researcher at Yale at the time and is currently an assistant professor at Arizona State University, and Nathaniel Bachtel, a graduate student at Yale School of Medicine. They conducted experiments on mice sensitized to exhibit allergic reactions to ova, a protein found in chicken eggs. As hypothesized, sensitized mice showed an inclination to avoid water contaminated with ova, unlike the control group, which showed a preference for such water. The behavioral aversion in sensitized mice was observed to last for an extended period.

Further investigation by the team revealed that this aversive behavior in mice allergic to ova could be altered by manipulating specific variables in the immune system. For example, when IgE antibodies were blocked, mice ceased avoiding water containing the allergenic protein. These IgE antibodies are pivotal in triggering mast cells, a specific white blood cell type, which in concert with other proteins in the immune system, plays a critical role in signaling brain areas governing aversion behavior. Without the initiating role of IgE, the information transmission was halted, and the mice no longer avoided the allergenic substance.

Medzhitov posited that these observations shed light on the evolutionary purpose of the immune system, which is to enable animals to evade hazardous environmental settings. Further understanding of how the immune system stores data on potential threats could, in the future, aid in mitigating excessive responses to a broad range of allergens and pathogens.

Reference: “Immune sensing of food allergens promotes avoidance behaviour” by Esther B. Florsheim, Nathaniel D. Bachtel, Jaime L. Cullen, Bruna G. C. Lima, Mahdieh Godazgar, Fernando Carvalho, Carolina P. Chatain, Marcelo R. Zimmer, Cuiling Zhang, Gregory Gautier, Pierre Launay, Andrew Wang, Marcelo O. Dietrich and Ruslan Medzhitov, published on July 12, 2023, in Nature.
DOI: 10.1038/s41586-023-06362-4

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More about Immune System and Behavior

• Yale School of Medicine
• Howard Hughes Medical Institute
• Journal Nature
• Immunobiology Research at Yale
• Allergic Reactions and the Immune System
• Defensive Behaviors in Animals
• Esther Florsheim’s Research Profile at Arizona State University
• Behavioral Modification and the Immune System: An Overview