Hyocholic acids shape neonatal immune tolerance and microbiota assembly.

Hyocholic acids dominate neonatal bile acids, constituting over 51% in meconium and shaping immune development during early life.

• Why it matters: Understanding how early-life immune tolerance develops is crucial for preventing inflammatory diseases, yet the role of specific bile acids like HCAs remains unclear.
• What they did: The study analyzed bile acid profiles in human newborns, revealing high HCA levels produced by fetal enzyme CYP3A7, which influence immune cell differentiation and microbiome assembly.
• The result: High neonatal HCA levels correlate with reduced infections and gastrointestinal issues, highlighting HCAs as key mediators in immune programming and potential targets for early disease prevention.