Programmed cell death ligand 2 regulates TH9 differentiation and induction of chronic airway hyperreactivity.

Background: Asthma is defined as a chronic inflammatory disease of the airways; however, the underlying physiologic and immunologic processes are not fully understood.

Objective: The aim of this study was to determine whether TH9 cells develop in vivo in a model of chronic airway hyperreactivity (AHR) and what factors control this development.

Method: We have developed a novel chronic allergen exposure model using the clinically relevant antigen Aspergillus fumigatus to determine the time kinetics of TH9 development in vivo.