Advancing protective effects of maternal antibodies in neonates through animal models.

Maternal immunity is critical for neonatal defense during early life, when infants are highly susceptible to infection. Antibodies transferred across the placenta or through breast milk not only provide immediate protection but also shape immune development. Defining the mechanisms and outcomes of this passive protection is essential for guiding maternal vaccination strategies and reducing the global burden of early-life infections. Animal models are indispensable for studying maternal antibody effects on neonatal immunity because they allow controlled investigation of transfer and protective functions that cannot be directly tested in humans. However, the mode of antibody transfer varies widely across species: humans rely primarily on placental IgG transfer, ungulates such as cows and pigs depend entirely on colostrum rich in IgG or IgA, and rodents acquire maternal antibodies both prenatally and postnatally. These species-specific differences highlight the importance of selecting appropriate models for distinct research questions. This review aims to highlight mechanisms of antibody transfer across species, identify factors that enhance or limit protection, and inform strategies to strengthen maternal immunization and improve neonatal health.