Although maternal antibodies protect newborn babies from infection^1,2, little is known about how protective antibodies are induced without prior pathogen exposure. Here we show that neonatal mice that lack the capacity to produce IgG are protected from infection with the enteric pathogen enterotoxigenic Escherichia coli by maternal natural IgG antibodies against the maternal microbiota when antibodies are delivered either across the placenta or through breast milk. By challenging pups that were fostered by either maternal antibody-sufficient or antibody-deficient dams, we found that IgG derived from breast milk was crucial for protection against mucosal disease induced by enterotoxigenic E. coli. IgG also provides protection against systemic infection by E. coli. Pups used the neonatal Fc receptor to transfer IgG from milk into serum. The maternal commensal microbiota can induce antibodies that recognize antigens expressed by enterotoxigenic E. coli and other Enterobacteriaceae species. Induction of maternal antibodies against a commensal Pantoea species confers protection against enterotoxigenic E. coli in pups. This role of the microbiota in eliciting protective antibodies to a specific neonatal pathogen represents an important host defence mechanism against infection in neonates.

尽管母源抗体可以保护新生儿免受感染^1,2 ，但对于在没有事先接触病原体的情况下如何诱导保护性抗体的情况知之甚少。在这里，我们发现，当抗体通过胎盘或通过母乳传递时，针对母体微生物群的母体天然 IgG 抗体可以保护缺乏产生 IgG 能力的新生小鼠免受肠道病原体产肠毒素大肠杆菌的感染。通过对母体抗体充足或抗体缺乏的母鼠培育的幼崽进行挑战，我们发现源自母乳的 IgG 对于预防产肠毒素大肠杆菌引起的粘膜疾病至关重要。 IgG 还可以防止大肠杆菌的全身感染。幼崽利用新生儿 Fc 受体将 IgG 从乳汁转移到血清中。母体共生微生物群可以诱导识别由产肠毒素大肠杆菌和其他肠杆菌科物种表达的抗原的抗体。针对共生泛菌属物种的母体抗体的诱导可以保护幼崽免受产肠毒素大肠杆菌的侵害。微生物群在引发针对特定新生儿病原体的保护性抗体方面的作用代表了针对新生儿感染的重要宿主防御机制。