High-dimensional immune profiling of atopic dermatitis reveals a dysfunctional OX40⁺ regulatory T cell subset

Background Atopic dermatitis (AD) is a chronic inflammatory skin disorder affecting up to 10% of the global population, characterized by eczematous lesions and intense pruritus. Although immune mechanisms in AD are increasingly recognized, the precise role of regulatory T cells (Tregs) remains controversial, with conflicting reports on their frequency and suppressive capacity. This study aimed to delineate immune dysregulation underlying AD, focusing on the heterogeneity and functional states of Tregs. Methods Utilizing a 39-parameter CyTOF panel, we analyzed peripheral blood mononuclear cells (PBMCs) from 48 AD patients and 48 healthy controls. Findings were validated using public single-cell RNA sequencing datasets of PBMCs and skin, in vitro suppression assays, and immunofluorescence staining of skin lesions. Results AD patients exhibited an increased frequency of circulating Tregs, accompanied by altered expression of markers linked to function and activation. We identified a distinct CLA⁺ Treg subset expressing OX40, which impairs Treg function, and CRTH2, a marker of type 2 immunity. The frequency of this OX40⁺CRTH2⁺ subset correlated with disease severity, suggesting that these CLA⁺ Tregs are functionally compromised in AD. These OX40⁺ Tregs displayed a Th2-skewed transcriptional signature and showed markedly reduced suppressive capacity in vitro compared to OX40⁺ Tregs from healthy controls. Conclusions These results provide novel insights into AD immunopathology and highlight OX40⁺ Tregs as key drivers of immune imbalance. Our findings provide a mechanistic rationale for emerging OX40-targeted therapies, supporting precision medicine approaches in AD treatment.