An Observational Study on the Correlation Between Circulating Cell-free DNA and Skin Macrophage STING Pathway Activation in Patients With Atopic Dermatitis

Scientific Rationale AD is primarily driven by Type 2 (Th2) immune responses; however, the role of innate immune sensing of damage-associated molecular patterns (DAMPs) in maintaining chronic inflammation is less defined. Cell-free DNA (cfDNA) has emerged as a potent DAMP in various autoimmune conditions. This study explores the hypothesis that cfDNA released during epidermal injury and inflammatory cell turnover in AD serves as a ligand for the cyclic GMP-AMP synthase (cGAS) - Stimulator of Interferon Genes (STING) pathway within the skin microenvironment.

Study Objectives Quantification of Systemic DAMPs: To quantify plasma cfDNA concentrations in a cohort of AD patients (n=40) compared to age- and sex-matched healthy controls (n=40) using fluorometric assays. Tissue-Level Mechanism: To characterize the local immune landscape via immunofluorescence (IF) staining of skin biopsies. The study focuses on the infiltration density of CD68+ macrophages and the expression/co-localization of STING protein within these cells.

Methodology Clinical Assessment: Patients undergo standardized dermatological evaluation to determine disease severity. Bio-sampling: Peripheral blood is collected for baseline hematology and cfDNA isolation. For a subset of patients, 4mm punch biopsies are taken from active lesional skin. Data Analysis: Cross-sectional analysis will be used to determine the diagnostic value of cfDNA and its ability to stratify disease severity (Moderate vs. Severe AD). Immunohistochemical quantification will be used to verify the activation of the STING pathway in situ.