Maternal antibodies regulate the establishment of murine oral and salivary mucosal immunity

Mucosal homeostasis after birth depends on coordinated interactions between the microbiota and the immune system, with barrier tissues employing distinct mechanisms. Here, we show that maternal Immunoglobulin G (IgG), transferred both in utero and via breastfeeding, reaches the murine neonatal salivary glands and is secreted into saliva, where it recognizes maternal oral microbes and regulates colonization. Offspring lacking in utero-derived IgG show heightened salivary T- and B-cell activation, followed by alterations in the IgG/IgA balance in adult saliva. While postnatal microbiota is essential for priming salivary adaptive immunity, perinatal IgG intrinsically restrains the adaptive responses independent of microbial load. In utero-derived IgG further shapes adult gingival immunity and limits destructive inflammation in murine periodontitis. By contrast, breast milk antibodies promote timely and proper epithelial maturation, a process dependent on microbial load. Thus, we uncover distinct yet complementary roles of pre- and postnatal maternal antibodies in governing oral immune development and long-term protection against oral disease.