BACKGROUND

Early administration of IL-6R blockade is effective in adult-onset Still's disease (AOSD), but the underlying immune alterations during combined immunotherapy remain unclear.

METHODS

We employed high-dimensional single-cell mass cytometry and an unbiased bioinformatics pipeline to characterize the immune landscape in treatment-naïve AOSD patients, stable AOSD patients after 24 weeks of IL-6R blockade plus methotrexate and prednisone, and matched healthy controls. Cytokine profiling was conducted using a high-throughput cytometric bead array, and potential regulatory networks were identified using the PerformanceAnalytics package. Validation was performed via flow cytometry and mRNA sequencing.

RESULTS

We identified 22 peripheral immune cell populations and characterized their composition and phenotypic markers. Treatment-naïve AOSD patients exhibited significant depletion of CD4 T cells and B cells, along with excessive activation of CD8 T cells and a previously unreported CD45CD3CD19CD10CD66a population, findings that were validated in an independent AOSD cohort. mRNA sequencing revealed the proinflammatory role of CD8 T cells. Notably, these dysregulated immune profiles were markedly restored following immunotherapy. IL-18, IL-21, and IFN-γ demonstrated strong associations with adaptive immune cells and AOSD clinical indices.

CONCLUSIONS

Combined IL-6R blockade effectively modulates immune dysregulation in refractory AOSD, reversing key pathological immune alterations and highlighting its therapeutic potential.