Maternal IgG Affects Brain Development of Mouse Pups

Maternal IgG is an immunoglobulin present in breast milk and has been shown to play a role in the development of the immune system in infants. The aim of this study was to investigate the effects of maternal IgG on brain development in mouse pups. Maternal IgG immunoreactivity was observed in microglial cells of the pup brain, peaking at postnatal 8 day. In particular, strong IgG immunoreactivity was observed in the microglia in the corpus callosum and cerebellar white matter. IgG stimulation of primary cultured microglia resulted in activation of the type I interferon feedback loop by Syk. Among the IgG subclasses, IgG2a was found to have a strong influence on microglia. Analysis of FcRn KO mice that were unable to take up IgG from their mothers revealed that these mice had abnormalities in the proliferation and/or survival of microglia, oligodendrocytes, and some types of interneurons. FcRn KO mice also exhibited abnormalities in social behavior and adaptation to novel environments. This study suggests that maternal IgG affects brain development in pups. Overall design: To comprehensively explore the molecular changes in IgG-stimulated microglia at transcriptome-wide level, the transcriptomic profiles were compared between IgG-stimulated microglia and untreated controls (n = 4 cultures/group).