Exacerbation of spontaneous autoimmune nephritis following regulatory T cell depletion in B cell lymphoma 2‐interacting mediator knock‐out mice

Regulatory T cells (T_regs) have been recognized as central mediators for maintaining peripheral tolerance and limiting autoimmune diseases. The loss of T_regs or their function has been associated with exacerbation of autoimmune disease. However, the temporary loss of T_regs in the chronic spontaneous disease model has not been investigated. In this study, we evaluated the role of T_regs in a novel chronic spontaneous glomerulonephritis model of B cell lymphoma 2‐interacting mediator (Bim) knock‐out mice by transient depleting T_regs. Bim is a pro‐apoptotic member of the B cell lymphoma 2 (Bcl‐2) family. Bim knock‐out (Bim^–/–) mice fail to delete autoreactive T cells in thymus, leading to chronic spontaneous autoimmune kidney disease. We found that T_reg depletion in Bim^–/– mice exacerbated the kidney injury with increased proteinuria, impaired kidney function, weight loss and greater histological injury compared with wild‐type mice. There was a significant increase in interstitial infiltrate of inflammatory cells, antibody deposition and tubular damage. Furthermore, the serum levels of cytokines interleukin (IL)?2, IL‐4, IL‐6, IL‐10, IL‐17α, interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α were increased significantly after T_reg depletion in Bim^–/– mice. This study demonstrates that transient depletion of T_regs leads to enhanced self‐reactive T effector cell function followed by exacerbation of kidney disease in the chronic spontaneous kidney disease model of Bim‐deficient mice.