Microenvironmental network of clonal CXCL13⁺CD4⁺ T cells and Tregs in pemphigus chronic blisters

BACKGROUND. Pemphigus, a rare autoimmune bullous disease mediated by antidesmoglein autoantibodies, can be controlled with systemic medication like rituximab and high-dose systemic corticosteroids combined with immunosuppressants. However, some patients continue to experience chronically recurrent blisters in a specific area and require long-term maintenance systemic therapy. METHODS. Skin with chronic blisters was obtained from patients with pemphigus. Immunologic properties of the skin were analyzed by immunofluorescence staining, bulk and single-cell RNA and TCR sequencing, and a highly multiplex imaging technique known as CO-Detection by indEXing (CODEX). Functional analyses were performed by flow cytometry and bulk RNA-Seq using peripheral blood from healthy donors. Intralesional corticosteroid was injected into patient skin, and changes in chronically recurrent blisters were observed. RESULTS. We demonstrated the presence of skin tertiary lymphoid structures (TLSs) with desmoglein-specific B cells in chronic blisters from patients with pemphigus. In the skin TLSs, CD4⁺ T cells predominantly produced CXCL13. These clonally expanded CXCL13⁺CD4⁺ T cells exhibited features of activated Th1-like cells and downregulated genes associated with T cell receptor–mediated signaling. Tregs are in direct contact with CXCL13⁺CD4⁺ memory T cells and increased CXCL13 production of CD4⁺ T cells through IL-2 consumption and TGF-β stimulation. Finally, intralesional corticosteroid injection improved chronic blisters and reduced skin TLSs in patients with pemphigus. CONCLUSION. Through this study we conclude that skin TLSs are associated with the persistence of chronically recurrent blisters in patients with pemphigus, and the microenvironmental network involving CXCL13⁺CD4⁺ T cells and Tregs within these structures plays an important role in CXCL13 production.