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The adaptive immune system in early life: The shift makes it count
Daan K J Pieren1, Mardi C Boer1, Jelle de Wit1
1Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, Netherlands.
Insights
Early life vaccination effectiveness is influenced by the infant immune system's innate-like and tolerogenic features. Understanding these immune characteristics can help improve infant vaccination strategies against infections.
Area of Science:
- Immunology
- Pediatrics
- Vaccinology
Background:
- Neonatal immune systems are naive, increasing susceptibility to life-threatening respiratory infections.
- While vaccines reduce childhood mortality, infant vaccination requires repeated doses and wanes faster than in adults.
- The infant immune system, once considered immature, now shows evidence of strong innate-like effector functions and a tolerogenic counterpart.
Purpose of the Study:
- To review recent literature on the adaptive immune system in early life.
- To explore how innate-like and tolerogenic features influence infant immune responses to vaccination.
- To propose the use of these immune features as biomarkers for improved infant vaccination strategies.
Main Methods:
- Literature review of recent studies on early life adaptive immunity.
- Analysis of the interplay between innate-like effector functions and tolerogenic mechanisms.
- Speculation on the developmental shift from innate-like/tolerogenic immunity to immune memory.
Main Results:
- The early life adaptive immune system exhibits potent innate-like effector functions for pathogen clearance.
- A tolerogenic arm of the adaptive system balances these effector functions to prevent damage.
- A developmental shift occurs from these early features towards immune memory formation.
Conclusions:
- The efficacy of infant vaccination may vary depending on the phase of immune development (innate-like, tolerogenic, or memory-focused).
- Identifying innate-like and tolerogenic immune features could serve as biomarkers.
- These biomarkers may enable the optimization of vaccination strategies for infants, enhancing protection against respiratory and other infections.
Abstract:
Respiratory infectious diseases encountered early in life may result in life-threatening disease in neonates, which is primarily explained by the relatively naive neonatal immune system. Whereas vaccines are not readily available for all infectious diseases, vaccinations have greatly reduced childhood mortality. However, repeated vaccinations are required to reach protective immunity in infants and not all vaccinations are effective at young age. Moreover, protective adaptive immunity elicited by vaccination wanes more rapidly at young age compared to adulthood. The infant adaptive immune system has previously been considered immature but this paradigm has changed during the past years. Recent evidence shows that the early life adaptive immune system is equipped with a strong innate-like effector function to eliminate acute pathogenic threats. These strong innate-like effector capacities are in turn kept in check by a tolerogenic counterpart of the adaptive system that may have evolved to maintain balance and to reduce collateral damage. In this review, we provide insight into these aspects of the early life's adaptive immune system by addressing recent literature. Moreover, we speculate that this shift from innate-like and tolerogenic adaptive immune features towards formation of immune memory may underlie different efficacy of infant vaccination in these different phases of immune development. Therefore, presence of innate-like and tolerogenic features of the adaptive immune system may be used as a biomarker to improve vaccination strategies against respiratory and other infections in early life.
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