Identification of IL-17F/frequent exacerbator endotype in asthma.

Background: Severe asthma might be associated with overexpression of T17 cytokines, which induce neutrophil recruitment via neutrophil-mobilizing cytokines in airways.

Objective: To study IL-17-related cytokines in nasal/bronchial biopsies from controls and mild asthmatics (MAs) to severe asthmatics (SAs) in relation to exacerbation rate.

Methods: Inflammatory cells and IL-17A, IL-17F, IL-21, IL-22, and IL-23 cells were examined by immunohistochemistry in cryostat sections of bronchial/nasal biopsies obtained from 33 SAs (21 frequent exacerbators [FEs]), 31 MAs (3 FEs), and 14 controls.