Engagement of S. aureus shifts the activation trajectory of neutrophils towards serial eating

Neutrophil recruitment and activation are essential for the control of microbial infections, yet how these cells adapt functionally upon entry into inflamed tissues remains incompletely understood. In particular, how temporal cues and direct interaction with the pathogen differentially shape neutrophil heterogeneity and effector functions remains poorly defined. Here, we employed in vivo time-stamping of tissue entry to disentangle time-dependent versus pathogen interaction-specific drivers of neutrophil heterogeneity during S. aureus skin infection. We show that canonical aging and activation markers progressively accumulated with increasing time since arrival in the inflamed tissue. Strikingly, however, phagocytic activity at the single-cell level was uncoupled from tissue dwell time and instead strictly correlated with each neutrophil's history of prior uptake of S. aureus. Furthermore, pathogen engagement induced an immediate shift towards a maximally activated phenotype. Therefore, neutrophil functional heterogeneity in infected tissues is governed less by residence time and more by discrete pathogen encounters which act as a key instructive event for subsequently enhanced phagocytosis. This suggests that the balance of microenvironmental and pathogen-derived cues tailors neutrophil activation in order to optimize antimicrobial clearance.