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Without immune system communication, the brain does not warn the body about potential dangers in the environment and does not try to avoid those threats, the study shows. Credit: Neuroscience News

Our Immune System May Help Guide Behavior

Summary: A recent study found the immune system plays a pivotal role in altering our behaviors, especially in response to allergic triggers.

Researchers found that the brain, when informed by the immune system about potential dangers, prompts the body to avoid those threats. The study used mice sensitized to an allergen found in chicken eggs, showing that blocking certain antibodies in the immune system could alter the allergic mice’s avoidance behavior.

This breakthrough understanding of the immune system’s role in memorizing potential hazards could help manage excessive reactions to allergens in the future.

Key Facts:

  1. The study shows that the immune system significantly influences our behaviors, particularly avoidance behaviors in response to allergens.
  2. Mice allergic to a protein in chicken eggs were used in the study, and their avoidance behavior was altered when certain immune responses were blocked.
  3. This research could aid in future development of treatments to control excessive immune reactions to allergens and other pathogens.

Source: Yale

Simply the smell of seafood can make those with an allergy to it violently ill — and therefore more likely to avoid it. The same avoidance behavior is exhibited by people who develop food poisoning after eating a certain meal.

Scientists have long known that the immune system played a key role in our reactions to allergens and pathogens in the environment, but it was unclear whether it played any role in prompting these types of behaviors towards allergic triggers.

Credit: Neuroscience News

According to Yale-led research published July 12 in the journal Nature, it turns out that the immune system plays a crucial role in changing our behaviors.

“We find immune recognition controls behavior, specifically defensive behaviors against toxins that are communicated first through antibodies and then to our brains,” said Ruslan Medzhitov, Sterling Professor of Immunobiology at Yale School of Medicine, investigator for the Howard Hughes Medical Institute, and senior author of the study.

Without immune system communication, the brain does not warn the body about potential dangers in the environment and does not try to avoid those threats, the study shows.

A team in the Medzhitov lab, led by Esther Florsheim, at the time a postdoctoral researcher at Yale and now an assistant professor at Arizona State University, and Nathaniel Bachtel, a graduate student at the School of Medicine, studied mice that had been sensitized to have allergic reactions to ova, a protein found in chicken eggs.

As expected, these mice tended to avoid water laced with ova, while control mice tended to prefer ova-laced water sources. The aversion to ova-laced water sources in sensitized mice lasted for months, they found.

The team then examined whether they could alter the behavior of sensitized mice by manipulating immune system variables. They found, for instance, that mice allergic to ova lost their aversion to the protein in their water if Immunoglobulin E (IgE) antibodies, produced by the immune system, were blocked.

IgE antibodies trigger the release of mast cells, a type of white blood cell that, along with other immune system proteins, plays a crucial role in communicating to areas of the brain that control aversion behavior.

Without IgE as an initiator, the transmission of information was interrupted, so that mice no longer avoided the allergen.

Medzhitov said that the findings illustrate how the immune system evolved to help animals avoid dangerous ecological niches. Understanding how the immune system memorizes potential dangers, he added, could one day help suppress excessive reactions to many allergens and other pathogens.

About this immune system and behavior research news

Author: Bess Connolly
Source: Yale
Contact: Bess Connolly – Yale
Image: The image is credited to Neuroscience News

Original Research: Closed access.
Immune sensing of food allergens promotes avoidance behaviour” by Ruslan Medzhitov et al. Nature


Immune sensing of food allergens promotes avoidance behaviour

In addition to its canonical function of protection from pathogens, the immune system can also alter behaviour. The scope and mechanisms of behavioural modifications by the immune system is not yet well understood.

Here, using mouse models of food allergy, we show that allergic sensitization drives antigen-specific avoidance behaviour.

Allergen ingestion activates brain areas involved in the response to aversive stimuli, including the nucleus of tractus solitarius, parabrachial nucleus, and central amygdala. Allergen avoidance requires IgE antibodies and mast cells but precedes the development of gut allergic inflammation.

The ability of allergen-specific IgE and mast cells to promote avoidance requires cysteinyl leukotrienes and growth and differentiation factor 15 (GDF15). Finally, a comparison of C57BL/6 and BALB/c mouse strains revealed a strong effect of the genetic background on the avoidance behaviour.

These findings thus point to antigen-specific behavioural modifications that likely evolved to promote niche selection to avoid unfavourable environments.

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