Defects in LC3-associated phagocytosis in mice are shown to result in systemic lupus erythematosus-like disease; dying cells are engulfed but not degraded in LAP-deficient mice, resulting in increased serum levels of autoantibodies and inflammatory cytokines, and evidence of kidney disease. Jennifer Martinez et al. provide evidence that defects in LC3-associated phagocytosis in mice result in a condition resembling the autoimmune disease systemic lupus erythematosus. Dying cells are engulfed but not degraded in mice deficient in LC3-associated phagocytosis, resulting in elevated serum anti-DNA antibodies, inflammatory cytokines, and kidney disease. The effect is independent of canonical autophagy. These findings suggest a link between the clearance of dying cells, autophagic processes, and inflammation in the control of systemic lupus erythematosus. Defects in clearance of dying cells have been proposed to underlie the pathogenesis of systemic lupus erythematosus (SLE)1. Mice lacking molecules associated with dying cell clearance develop SLE-like disease2, and phagocytes from patients with SLE often display defective clearance and increased inflammatory cytokine production when exposed to dying cells in vitro. Previously, we3,4,5,6 and others7 described a form of noncanonical autophagy known as LC3-associated phagocytosis (LAP), in which phagosomes containing engulfed particles, including dying cells3,4,7, recruit elements of the autophagy pathway to facilitate maturation of phagosomes and digestion of their contents. Genome-wide association studies have identified polymorphisms in the Atg5 (ref. 8) and possibly Atg7 (ref. 9) genes, involved in both canonical autophagy and LAP3,4,5,6,7, as markers of a predisposition for SLE. Here we describe the consequences of defective LAP in vivo. Mice lacking any of several components of the LAP pathway show increased serum levels of inflammatory cytokines and autoantibodies, glomerular immune complex deposition, and evidence of kidney damage. When dying cells are injected into LAP-deficient mice, they are engulfed but not efficiently degraded and trigger acute elevation of pro-inflammatory cytokines but not anti-inflammatory interleukin (IL)-10. Repeated injection of dying cells into LAP-deficient, but not LAP-sufficient, mice accelerated the development of SLE-like disease, including increased serum levels of autoantibodies. By contrast, mice deficient in genes required for canonical autophagy but not LAP do not display defective dying cell clearance, inflammatory cytokine production, or SLE-like disease, and, like wild-type mice, produce IL-10 in response to dying cells. Therefore, defects in LAP, rather than canonical autophagy, can cause SLE-like phenomena, and may contribute to the pathogenesis of SLE.

RETRACTED ARTICLE: Noncanonical autophagy inhibits the autoinflammatory, lupus-like response to dying cells