Plasma Proteome-Driven Identification of Druggable Immune Regulators of Alopecia Areata, Validated by Transcriptome and Single-Cell Mapping.

INTRODUCTION

Alopecia areata (AA) is an autoimmune hair-loss disorder driven by aberrant T-cell activation and immune-epithelial crosstalk. To identify actionable upstream regulators, we established a proteome-anchored multi-omics framework integrating genetic instruments, lesional transcriptomics, and single-cell immune profiling.

METHODS

Putative causal plasma proteins were prioritized using cis-protein quantitative trait loci-based inference across two large proteomic datasets (UKB-PPP and deCODE). Candidates were validated by differential expression in AA lesions, protein-interaction networks, and cell-type-resolved expression from scalp single-cell RNA-seq. Druggability was assessed using curated pharmacological resources, and PheWAS evaluated safety-relevant pleiotropy.

RESULTS

The pipeline identified 206 and 169 AA-associated proteins, with CD28, GZMB, and CD1C emerging as convergent immune regulators. Single-cell data showed enrichment of CD28+ effector T cells and CD1C+ myeloid subsets in lesions, linking circulating protein signals with local inflammation. Transcriptomic patterns implicated IL-2-modulated CD28 signaling and antihistamine-responsive pathways. Druggability analyses highlighted belatacept, a CD28-blocking biologic, while PheWAS indicated minimal adverse-phenotype enrichment.

CONCLUSION

This proteome-driven framework uncovers druggable immune regulators of AA, positioning CD28 as an actionable target with a favorable safety profile and providing a generalizable strategy for autoimmune target discovery.