Pathogenesis of neutrophilic asthma mediated by Th1 and Th17 cells. The development of neutrophilic asthma is associated with subtypes of CD4+ T cells including Th1 and Th17 cells. Th1 cells are involved in mediating the infiltration of neutrophils and the formation of emphysematous lung. T-bet, STAT1, and STAT4 are transcriptional factors in Th1 cells. Th17 cells play critical roles in neutrophil infiltration, airway remodeling, collagen deposition, and airway hyperresponsiveness. RORγt and STAT3 are transcriptional factors in Th17 cells. Text color: Black, cytokine; Red, chemokine; Blue, anti-protease. T-bet, T-box protein expressed in T cells; RORγt, RAR-related orphan receptor gamma; CXCL, C-X-C motif chemokine ligand; SLPI, secretory leukocyte peptidase inhibitor. The figure was created using BioRender.com (accessed on 6 September 2021).