LPS and β-Glucan Induce Differential Memory-like Inflammatory Responses with Enhanced Reactivity in Neonatal Neutrophils Compared to Adults

Neutrophils are key effectors of innate immunity. Although traditionally regarded as short-lived effector cells, recent evidence suggests they can undergo functional reprogramming after microbial stimulation, leading to trained immunity. We investigated whether lipopolysaccharide (LPS) or Candida albicans β-glucan induces memory-like inflammatory responses in adult peripheral and neonatal cord blood neutrophils. We used complementary molecular and functional approaches to characterize neutrophil responses following in vitro priming with LPS or β-glucan and subsequent LPS restimulation. Cytokine secretion, reactive oxygen species (ROS) production, glycolytic activity (via lactate production and glycolytic enzyme expression), and ERK1/2 and NF-κB signaling pathway activation were assessed. Priming with LPS or β-glucan enhanced neutrophil responsiveness to secondary stimulation, resulting in increased secretion of IL-1β, IL-6, IL-8, CXCL1, and CCL2, together with elevated ROS production. These effects were consistently more pronounced in neonatal than in adult neutrophils. Memory-like neutrophils also exhibited metabolic reprogramming, associated by increased hexokinase-2 and phosphofructokinase-1 mRNA expression, elevated lactate production, and enhanced ERK1/2 and NF-κB activation. Human neutrophils, particularly neonatal cells, develop memory-like characteristics following LPS or β-glucan priming, highlighting their functional and metabolic plasticity and suggesting a role for neutrophil training in early-life immune adaptation.