Maternal antibodies orchestrate the establishment of salivary and oral mucosal immunity

The establishment of mucosal homeostasis after birth involves mutual development of the microbiota and the immune system, with each mucosal barrier has specific mechanisms. Here, we show that in utero-delivered maternal IgG antibodies are translocated to the salivary glands and secreted to the neonatal saliva. As a result, the microbial burden of the neonate oral cavity and salivary glands is reduced. In the absence of maternal antibodies, oral dendritic cells migrate in higher frequencies to the salivary glands resulting in elevated activation of T and B cells, while dampening T regulatory cells. The IgG/IgA balance in the adult saliva was also dysregulated. The absence of maternal antibodies further regulates the adult gingival immunity, a key oral barrier, increasing alveolar bone loss during experimental periodontitis. This work reveals the importance of the salivary-oral axis during neonatal life via maternal antibodies, orchestrating local mucosal immunity and protecting against pathological damage in adulthood. Overall design: B cell-deficient (JhT-/- ) females were crossed with wild-type (WT) males to generate offspring with intact B cells that were not exposed to mIg.