B-Cell Involvement in Immune Checkpoint Inhibitor-Induced Lichen Planus: A Comparative Analysis with Non-Drug-Related Lichen Planus

Background Immune checkpoint inhibitors (ICI) have significantly improved cancer prognosis but can lead to immune-related adverse events (irAE), including cutaneous manifestations affecting 30% to 60% of ICI-treated patients. However, the physiopathology of cutaneaous irAE remains unclear. Objective This study investigated the immune infiltration in tissues affected by cutaneous irAE to elucidate their contribution to the pathogenesis of these toxicities. Methods Skin biopsies from 6 patients with ICI-induced lichenoid eruptions were compared using imaging mass cytometry to samples from 7 controls with non-drug-related lichen planus. Results T cells were the predominant cell type within the inflammatory infiltrate in all samples, but we observed a reduced T-cell infiltration and an increased B-cell frequency in ICI-induced lichen planus compared to non-drug related lichen planus. Among B cells, we observed a significant decrease in IgD-CD27-double-negative B cells and an increase in IgD+CD27-naïve B cells. Spatial analysis demonstrated that infiltrating B cells were organized in aggregates close to T cells in ICI-induced lichen planus. Limitations This is a retrospective single-center study with a relatively small sample size. Conclusion This study sheds light on the involvement of B cells in the pathogenesis of ICI-induced lichen planus, suggesting distinct immunological mechanisms from non-drug-related lichen planus. CAPSULE SUMMARY ### Competing Interest Statement The authors have declared no competing interest.