Researchers have found that in asthma patients, ILC2 differentiates and matures through specific transcription factors RORα and GATA-3, and under the stimulation of IL-25, IL-33 and TSLP, it secretes a large amount of type 2 cytokines IL-5, IL-9, IL-1322, which is immunological mechanism of pathogenicity. Here, IL9 is linked to asthma.