Figure 1.

Schematic representation of priming mechanisms in innate immune cells during infancy. The microbiome and the perinatal environment challenge the innate immune system through PAMPs and DAMPs (left), driving epigenetic changes that promote metabolic reprogramming (middle). Upon re-challenge, either trained immunity or tolerance effects may be observed (right). In short-lived neutrophils, it remains unclear, whether “continuous priming” is necessary. If so, a stable microbiome could greatly influence these adaptive responses.