Phagocytosis Events Shift the Activation Trajectory of Neutrophils towards Serial Eating of S. aureus

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 neutrophils history of prior phagocytosis. Furthermore, pathogen uptake 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, with phagocytosis itself acting as a key instructive event. This balance of microenvironmental and pathogen-derived cues could tailor neutrophil activation in order to optimize antimicrobial clearance.