Influence of maternal microbiota during pregnancy on infant immunity

Abstract

Microbiota from various maternal sites, including the gut, vagina and breast milk, are known to influence colonization in infants. However, emerging evidence suggests that these sites may exert their influence prior to delivery, in turn influencing fetal immune development. The dogma of a sterile womb continues to be challenged. Regardless, there is convincing evidence that the composition of the maternal gut prior to delivery influences neonatal immunity. Therefore, while the presence and function of placental microbiome is not clear, there is consensus that the gut microbiota during pregnancy is a critical determinant of offspring health. Data supporting the notion of bacterial translocation from the maternal gut to extra-intestinal sites during pregnancy are emerging, and potentially explain the presence of bacteria in breast milk. Much evidence suggests that the maternal gut microbiota during pregnancy potentially determines the development of atopy and autoimmune phenotypes in offspring. Here, we highlight the role of the maternal microbiota prior to delivery on infant immunity and predisposition to diseases. Moreover, we discuss potential mechanisms that underlie this phenomenon.

The immunology of the fetal–placental unit comes of age

“…The authors examine the evidence from their group and others that indicate how the hormonal balance during pregnancy is tuned to maintain neutrophils capable of recognizing and attacking pathogens, while limiting NET generation and bystander injury of surrounding tissues. The authors' seminal work highlighted the association of aberrant NET generation with pre-eclampsia [9,12] while providing evidence in animal models that NETs could contribute to placental dysfunction [4]. The authors' seminal work highlighted the association of aberrant NET generation with pre-eclampsia [9,12] while providing evidence in animal models that NETs could contribute to placental dysfunction [4].…”

“…A still-controversial uterine microbiota could help to model the interaction between the feto-placental unit and the maternal immune system [1,12]. A still-controversial uterine microbiota could help to model the interaction between the feto-placental unit and the maternal immune system [1,12].…”

“…Indeed, neutrophil ability to generate NETs, controlled by bioactive microvesicles, is responsible for extensive microvascular injury and maladaptive tissue remodeling [8]. The authors' seminal work highlighted the association of aberrant NET generation with pre-eclampsia [9,12] while providing evidence in animal models that NETs could contribute to placental dysfunction [4]. It is interesting to note that low molecular weight heparins, widely used on an empirical basis at low prophylactic doses to prevent pregnancy complications in high-risk patients, influence the metabolic status of neutrophils.…”

“…The maternal microbiota from the intestine, vagina and milk is the primary source for the microbial colonization of infants. Recent evidence reviewed in this issue [12] indicates that microbial moieties exert their influence before birth and influence the immune response of the newborns, determining the health of the offspring.…”

“…A still-controversial uterine microbiota could help to model the interaction between the feto-placental unit and the maternal immune system [1,12]. The mechanisms by which the maternal microbiota influence the feto-placental unit during pregnancy, shaping the developing immune system of the infant, remains largely to be identified [12]. It might be relevant that decidual cells express innate pattern recognition receptors (e.g.…”