Pollutant particle priming amplifies airway compartment specific neutrophil and macrophage inflammatory programs following house dust mite acute exposure.

Real world inhalation exposures occur as temporally staggered mixtures of environmental pollutants and indoor allergens, yet the mechanistic consequences of sequential exposure remain poorly defined. Here, we investigated whether diesel exhaust particle (DEP) exposure primes the lung to alter subsequent responses to house dust mite (HDM) allergen independently of direct co-exposure or preexisting sensitisation. Using a murine model with defined temporal separation between exposures, we combined compartment resolved bulk transcriptomics and targeted single cell profiling to map inflammatory and cellular responses across lung tissue and airway lumen. DEP priming significantly amplified leukocyte recruitment following HDM challenge, with a dominant increase in neutrophils and no corresponding eosinophilic response. Transcriptomic analyses revealed that DEP alone preferentially induced NF-κB associated inflammatory programs, while HDM triggered both NF-κB and interferon (IFN) associated transcriptional responses. Importantly, DEP priming qualitatively reprogrammed the allergen response, enhancing both IFN stimulated gene (ISG) expression and pro-inflammatory cytokine networks. These effects were most pronounced in the airway luminal compartment, indicating a prominent inflammatory niche shaped by recruited immune cells. Single cell analyses identified expansion and activation of multiple neutrophil subpopulations, alongside recruitment of macrophage subsets, NK cells, and CD8