Abstract
With birth, the newborn is transferred from a quasi-sterile environment to the outside world. At this time, the neonatal immune system is inexperienced and continuously subject to a process of development as it encounters different antigenic stimuli after birth. It is initially characterized by a bias toward T helper 2 phenotype, reduced T helper 1, and cytotoxic responses to microbial stimuli, low levels of memory, and effector T and B cells and a high production of suppressive T regulatory cells. The aim of this setting, during fetal life, is to maintain an anti-inflammatory state and immune-tolerance. Maternal antibodies are transferred during pregnancy through the placenta and, in the first weeks of life of the newborn, they represent a powerful tool for protection. Thus, optimization of vaccination in pregnancy represents an important strategy to reduce the burden of neonatal infections and sepsis. Beneficial effects of maternal immunization are universally recognized, although the optimal timing of vaccination in pregnancy remains to be defined. Interestingly, the dynamic exchange that takes place at the fetal-maternal interface allows the transfer not only of antibodies, but also of maternal antigen presenting cells, probably in order to stimulate the developing fetal immune system in a harmless way. There are still controversial effects related to maternal immunization including the so called “immunology blunting,” i.e., a dampened antibody production following infant's vaccination in those infants who received placentally transferred maternal immunity. However, clinical relevance of this phenomenon is still not clear. This review will provide an overview of the evolution of the immune system in early life and discuss the benefits of maternal vaccination. Current maternal vaccination policies and their rationale will be summarized on the road to promising approaches to enhance immunity in the neonate.
Highlights
Despite significant advances in child survival in the last few decades, infectious diseases continue to be among the main causes of morbidity and mortality, especially in the neonatal period [1]
To retrieve information for this review, a PubMed based research was conducted using the medical subject heading database terms “vaccination” OR “immunization” AND “pregnancy.” In addition, maternal, fetal, immune system, placenta, neonate were used as search terms
This phenomenon, called “blunting,” has been associated to the antibodies transferred by the mother to the fetus after vaccination, and to those generated in response to natural infection before or during pregnancy
Summary
Edited by: Vassiliki Papaevangelou, National and Kapodistrian University of Athens, Greece. The newborn is transferred from a quasi-sterile environment to the outside world At this time, the neonatal immune system is inexperienced and continuously subject to a process of development as it encounters different antigenic stimuli after birth. The neonatal immune system is inexperienced and continuously subject to a process of development as it encounters different antigenic stimuli after birth It is initially characterized by a bias toward T helper 2 phenotype, reduced T helper 1, and cytotoxic responses to microbial stimuli, low levels of memory, and effector T and B cells and a high production of suppressive T regulatory cells. Maternal antibodies are transferred during pregnancy through the placenta and, in the first weeks of life of the newborn, they represent a powerful tool for protection. Current maternal vaccination policies and their rationale will be summarized on the road to promising approaches to enhance immunity in the neonate
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