Upregulation of IL-9 and JAK-STAT signaling pathway in children with autism

Autism spectrum disorder (ASD) gradually develops predominantly neurodevelopmental disorders, which are socially diagnosed in early childhood. Though the etiopathology of ASD is not clear, immune alteration has been suggested as autism's pathophysiological mechanism. Previous studies found that several cytokines and transcription factor activation pathways were significantly increased in ASD. IL-9 has been confirmed to play a significant role in the central nervous system (CNS). The aim of the present study was to investigate the understudied role of pro- and anti-inflammatory cytokines and the JAK-STAT signaling pathway in ASD. We examined the IL-1β, IL-4, IFN-γ, and IL-9 positive immunostaining in all cells, and CD4⁺ T cells, in ASD and normally developing control children (TD), on peripheral blood mononuclear cells (PBMCs), using flow cytometry. We explored PBMC mRNA expression levels for IL-1β, IL-4, IFN-γ, IL-9, JAK1, and STAT5, by using real-time PCR (RT-PCR). We also explored PBMC protein expression levels for IL-1β, IL-4, IL-9, pJAK1, and pSTAT5 by using western blotting. We found that the children with ASD had increased IL-1β, IL-4, IFN-γ, and IL-9 positive immunostaining in all cells, and in CD4⁺ cells, relative to the TD controls. The mRNA and protein expression for IL-1β, IL-4, IFN-γ, IL-9, JAK1, pJAK1, STAT5, and pSTAT5 were also significantly elevated in ASD relative to TD controls. These results suggested that cytokines and JAK-STAT activation signaling have an essential role in immune dysfunction in ASD.