Scientists Discover Allergies Build Up, Nerve Cells Keep a ‘Memory’ of Those Irritants

Scientists have found a likely explanation for why allergies seem to grow and spread over time — and it starts in the nervous system, not just the immune system.In a study published last month in the journal “Cell,” researchers at the Ragon Institute of Mass General Brigham, MIT, and Harvard University found that sensory neurons — the nerve cells responsible for touch — can develop something like a memory of allergens. Each time these neurons encounter an allergen, they become more reactive, amplifying the body’s allergic response.“We therefore hypothesized that recurrent low-dose protease allergen exposure would induce a neuron-intrinsic ‘memory’ or trained state that gives rise to neuroimmune memory,” the researchers wrote. “Allergen-induced neuroimmune memory promotes responsiveness to recurrent allergen exposure in an antigen-independent manner.”This builds on earlier work. In a 2020 study, immunologist Caroline Sokol and her team of researchers first linked environmental allergic reactions to sensory neurons, discovering that these cells respond directly to allergens by triggering an itch response. What remained unclear until now was how that reaction intensifies with repeated exposure.To find out, the researchers exposed mice to allergy triggers, including a papaya-derived compound called papain and dust mite particles. They discovered that these exposures shifted the mice’s neuronal mitochondria — the structures that generate energy for cells — into a “primed,” hypervigilant state. When the mice encountered the allergen again, their nerve cells triggered a stronger immune response and more intense itching than before.Notably, this priming effect wasn’t limited to a single allergen. Mice first exposed to papain reacted more strongly when later exposed to dust mites or mold. Still, the study has limits. It focused specifically on skin inflammation and itching in mice, so it’s not yet confirmed whether the same process drives other allergic conditions, like food allergies or asthma, or whether it works identically in humans.Ms. Sokol’s team is now working to pin down exactly how this neuronal sensitization takes hold and why it leads to full-blown allergies in some cases but not others. They’ve already identified a mitochondrial protein that appears central to the process, raising the possibility of future drugs that target the mechanism directly.

Scientists Discover Allergies Build Up, Nerve Cells Keep a ‘Memory’ of Those Irritants

Scientists Discover Allergies Build Up, Nerve Cells Keep a ‘Memory’ of Those Irritants

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