Genome-wide DNA methylation changes in maternal immune cells from MMC+ and MMclow offspring mice

During mammalian pregnancy, immune cells are vertically transferred from mother to fetus. The functional role of these maternal microchimeric cells (MMc) is largely unknown. We show that MMc induce a preferential differentiation of hematopoietic stem and progenitor cells towards myelopoiesis in bone marrow of fetal mice, and improves resilience against cytomegalovirus infection in neonates. In humans, low MMc counts in cord blood are associated with an increased number of infections in the first year of life primarily in male newborns. Taken together, MMc boost neonatal immunity in mice and humans to mitigate the risk for early life infections.