Iron Deficiency Drives Th2-Mediated Immunity in Pediatric Atopic Dermatitis Through DNA Hypermethylation and TIGIT Suppression in IL-10-Producing Breg Cells.

Background: Pediatric atopic dermatitis (AD), a common chronic relapsing inflammatory skin disorder, often co-occurs with iron deficiency. However, the causal relationship and mechanisms linking iron homeostasis to AD pathogenesis remain unclear. This study investigates etiopathogenetic role of iron deficiency in childhood AD by analyzing molecular pathways and clinical impacts on disease progression. Methods: We have enrolled 298 pediatric AD patients based on the Hanifin and Rajka criteria to evaluate the relationship between peripheral iron and the severity of AD, as well as the levels of serum iron, ferritin, and transferrin in children with AD. The percentages of Th2 cells and IL-10-producing CD24+CD38+CD19+ regulatory B (Breg) cells were quantified by flow cytometry. RNA-sequencing and bioinformatic analysis were performed to explore the iron deficiency-sensitive genes in CD19+ B cells treated with Ciclopiroxolamine (CPX). The differentially expressed genes, including T cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif (ITIM) domain (TIGIT) and IL10, were further confirmed by RT-qPCR. 5-mC level was determined to evaluate the effect of iron deficiency on DNA methylation. TIGIT was inhibited in CD19+ B cells using a blocking antibody to assess its regulatory role in Breg cells. Results: Children with severe AD have lower levels of iron ions in peripheral blood compared with the mild patients (P<0.0001). Children with AD exhibited decreased serum levels of iron (P<0.01), ferritin (P< 0.01), and transferrin (P<0.05), along with an elevated percentage of Th2 cells (P<0.01) and reduced CD24+CD38+CD19+ Breg cells (P<0.01). CPX-mediated iron chelation suppressed IL-10-producing Breg cells (P<0.01) by inducing DNA methylation (P<0.05) and downregulating TIGIT (P<0.001), while promoting the expansion of IL-4-producing Th2 cells (P<0.05). Conclusion: Iron deficiency contributes to Th2 cell expansion in pediatric AD via DNA methylation and TIGIT suppression in IL-10-producing Breg cells.