"What struck me most was that these Paneth cell changes were present in allergen-naive mice—the animals had never been exposed to peanut," Clough said. "This tells us the gut is already in an altered state before any allergic challenge. The barrier defect may come first, and allergy follows."

How does one missing protein cascade into allergy?

Beyond the Paneth cell defect, the atlas — built from thousands of individual epithelial cells in susceptible CC027 mice and resistant C3H/HeJ mice — identified 13 distinct cell populations and revealed a coordinated pattern of gut-lining remodeling present before any allergen exposure:

• A novel population of interferon-responsive absorptive enterocytes was significantly depleted, suggesting weakened antiviral and immune surveillance.
• Goblet cells, which build the protective mucus barrier, expanded, while enteroendocrine cells, which regulate permeability signaling, declined.
• Tuft cells, key initiators of type 2 allergic immune responses, increased and showed elevated expression of allergic immune receptors, including IL-4Rα.
• Electron microscopy showed Paneth cells under cellular stress, with dilated endoplasmic reticulum and misshapen secretory granules, consistent with secretory dysfunction.

The consequences reach into the microbiome. Lysozyme normally eliminates bacteria that promote allergic immune responses. Mice engineered to lack Lyz1 and allergy-susceptible CC027 mice shared enrichment of the same bacterial genera, including Ruminococcus and Akkermansia — evidence that losing lysozyme shifts the microbial community toward type 2, or allergic, immune skewing, tuft and goblet cell expansion, and increased intestinal permeability.

"This study repositions the intestinal epithelium as a possible primary driver of allergic susceptibility, not a passive bystander," Steinbach said. "A genetic loss of a single antimicrobial protein in Paneth cells cascades into microbiome changes, immune skewing, and a gut barrier primed for allergy. That is a mechanistic chain in which we can potentially intervene."

Why it matters for patients and families

Peanut allergy causes the majority of fatal food-induced anaphylaxis cases in the United States. Current management depends on strict avoidance and emergency epinephrine; oral immunotherapy can desensitize some patients, but sustained tolerance remains out of reach. If the epithelial and microbial roots of susceptibility can be corrected before a child's first allergen exposure, allergy might be prevented rather than managed.

"My son has a life-threatening peanut allergy, and for our family, like most other families living with peanut allergy, every meal is a calculation," Sheikh said. "This research gives us a new framework for asking why the gut becomes susceptible in the first place and ultimately for designing interventions that could protect children before their first allergic reaction."

The findings remain preliminary. The pediatric biopsy data come from a comparison that shows an association, not proof that lysozyme deficiency causes peanut allergy in children, and the mechanistic work rests on mouse models. The team next plans to confirm the results in a larger pediatric cohort and use human intestinal organoids — lab-grown miniature guts — to test whether correcting lysozyme deficiency or microbiome composition can restore barrier function.