Tocilizumab monotherapy uncovered the role of the CCL22/17-CCR4⁺ Treg axis during remission of crescentic glomerulonephritis

Objectives: Tocilizumab (TCZ) is a humanised anti-interleukin (IL)-6 receptor (IL-6R) monoclonal antibody that is a promising agent to treat various autoimmune diseases. However, the mechanism of TCZ efficacy is unclear. This study aims to elucidate the relationship between Tregs and IL-6R blockade in autoimmunity-mediated renal disease based on a TCZ-treated cohort of patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and in an experimental model of crescentic glomerulonephritis (cGN). Methods: We examined multiple serum levels of cytokines and chemokines and peripheral blood mononuclear cells in patients with AAV who received TCZ monotherapy and achieved drug-free remission. Moreover, we investigated the mechanistic role of IL-6R blockade in accelerated cGN model to analyse the local sites of inflammation. Results: Serum chemokines CCL22 and CCL17, in addition to the CCR4⁺Foxp3⁺ Treg population, increased in patients who demonstrated drug-free remission after the cessation of TCZ. In the cGN model, IL-6R blockade ameliorated the disease, elevated CCL22/17 in CD206⁺CD11b⁺CD11c⁺ kidney M2-like type macrophages, and increased the migration of Tregs into the kidney and regional lymph nodes. The local administration of CCL22 in the kidney facilitated Treg accumulation and reduced glomerular crescent formation. Conclusions: This study revealed a new mechanism whereby effector Tregs migrate into the inflammatory kidney via the CCL22/17–CCR4 axis that is facilitated by M2-like type macrophages that are induced by IL-6R blockade.