Tsai et al. demonstrate that loss of Bim (BCL2L11) in myeloid cells in mice (LysM CreBim fl/fl) is sufficient to induce systemic autoimmunity. Kidney macrophages in LysM CreBim fl/fl mice possess a proinflammatory transcriptional signature and signal through TRIF to cause end-stage glomerulonephritis.
The Bcl-2 family is considered the guardian of the mitochondrial apoptotic pathway. We demonstrate that Bim acts as a molecular rheostat by controlling macrophage function not only in lymphoid organs but also in end organs, thereby preventing the break in tolerance. Mice lacking Bim in myeloid cells (LysM CreBim fl/fl) develop a systemic lupus erythematosus (SLE)–like disease that mirrors aged Bim −/− mice, including loss of marginal zone macrophages, splenomegaly, lymphadenopathy, autoantibodies (including anti-DNA IgG), and a type I interferon signature. LysM CreBim fl/fl mice exhibit increased mortality attributed to glomerulonephritis (GN). Moreover, the toll-like receptor signaling adaptor protein TRIF (TIR-domain–containing adapter-inducing interferon-β) is essential for GN, but not systemic autoimmunity in LysM CreBim fl/fl mice. Bim-deleted kidney macrophages exhibit a novel transcriptional lupus signature that is conserved within the gene expression profiles from whole kidney biopsies of patients with SLE. Collectively, these data suggest that the Bim may be a novel therapeutic target in the treatment of SLE.