Early-life microbiota direct an epithelial S100 program required for neonatal immunity.

Early-life microbiota induce epithelial S100A9 expression, crucial for neonatal immunity, with calprotectin rescuing microbiota-depleted pups from sepsis.

• Why it matters: Understanding how neonatal immune responses develop is vital because early-life immunity differs from adults, and infections can be deadly during this period.
• What they did: The study examined neonatal mice, showing that microbiota exposure at birth triggers intestinal epithelial cells to produce S100A9, with probiotic bacteria like Lactobacillus and metabolites like indole-3-lactic acid playing key roles.
• The result: Neonatal pups lacking epithelial S100A9 were highly susceptible to infection, but administering calprotectin or probiotics restored defense, highlighting potential strategies to prevent neonatal sepsis.