Role of immune cells in seborrheic dermatitis: a two-sample bidirectional Mendelian randomization study

Prior research has indicated a link between seborrheic dermatitis (SD) and dysregulated immune responses; however, the causal linkage between this association and certain immune cell features has yet to be thoroughly clarified. This study seeks to examine the potential causal influence of immune cell characteristics on the pathogenesis of seborrheic dermatitis (SD) and to evaluate if these characteristics can function as biomarkers for early diagnosis and therapy. Data mining was performed using the Genome-Wide Association Study (GWAS) Catalog database to select 731 immune cell features for exposure variables and seborrheic dermatitis for the outcome variable in a forward Mendelian Randomization (MR) study. In a reverse MR analysis, seborrheic dermatitis was designated as the exposure factor, while the significant immune cell traits recognized by a forward MR analysis were used as outcome factors to exclude potential reverse causality. Five MR analyses were carried out by utilizing methods such as inverse variance weighting (IVW). Additionally, false discovery rate (FDR) correction, heterogeneity testing, level-dependent pleiotropy analysis, and sensitivity analysis were conducted. This study identified 11 immune traits causally associated with seborrheic dermatitis (SD). Specifically, five immune phenotypes were found to have been linking to a lower risk of SD: CD24on transitional, CD28 - DN(CD4 - CD8-)%T cell, CD45RA - CD28 - CD8br AC, Resting Treg%CD4, SSC - A on NKT. Conversely, six immunized traits have been shown with a greater risk of SD: CD127 - CD8br AC, CD20on CD24 + CD27+, CD27on IgD - CD38br, CD27on unsw mem, CD28 + DN(CD4 - CD8-)%T cell, HLA DR on CD33br HLA DR + CD14dim. The sensitivity analysis showed an absence of heterogeneity and level-dependent pleiotropy.This study demonstrates that specific immune cell traits not only correlate with SD but also provide valuable mechanistic insights into its pathogenesis. These immune traits also hold promise as biomarkers for early diagnosis, risk stratification, and personalized therapy. In addition, the findings provide new insights into immune mechanisms, highlighting the potential of targeted immunotherapies in SD treatment.