Early Modulation of the Immune System: A Role for Early Life Microbiota Colonization

Accumulating evidence suggests that pregnancy and early life are sensitive time periods, during which, intrauterine and early life exposures (including microbiome) can modulate organs and immune system development, conferring a long-lasting effect on the developing newborn: facilitating tolerance to environmental exposures or contributing to the development of diseases in later life, including asthma, allergy and other immune-mediated diseases such as Inflammatory Bowel Disease.

One major event occurring during this sensitive time period is bacterial colonization. Pregnancy and early life are a critical period during which contact with microbes and specific microbe-associated metabolites are essential for the priming of the immune system development and maturation. While it has long been recognized that important exposures such as mode of delivery and feeding can contribute to bacterial colonization, it is now increasingly thought that maternal health status may also play a role, and that disease transmission can also occur through the microbiome. One of such diseases, where the gut microbiome may have a pivotal role, is inflammatory bowel disease. The MECONIUM study (Exploring MEChanisms Of disease traNsmission In Utero through the Microbiome) is a prospective study that aims to better understand how maternal microbiome and different exposures in early life may affect newborn bacterial colonization, and which consequences on the immune system development this may pose. Several other cohorts in other diseases, are ongoing, and will offer the opportunity to unravel 1) how aberrant early life colonization can lead to defects in the development and training of specific immune subsets and affect risk of disease, and 2) how microbiome modulation during this window of opportunity may foster the development of a healthy microbiome, thereby contributing to disease prevention.