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Interleukin-3 amplifies acute inflammation and is a potential therapeutic target in sepsis

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Science  13 Mar 2015:
Vol. 347, Issue 6227, pp. 1260-1265
DOI: 10.1126/science.aaa4268

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A new therapeutic target for sepsis

Infections can sometimes unleash powerful immune responses that careen out of control, leading to sepsis, organ failure, and death. Although antibiotics can help to quash the infection, sepsis patients also need therapies that will rein in the immune response. Weber et al. now identify one potential target, the secreted protein interleukin-3 (IL-3) (see the Perspective by Hotchkiss). In sepsis patients, higher serum concentrations of IL-3 were correlated with higher rates of mortality. In septic mice, IL-3 caused the immune system to produce large amounts of cells called monocytes and neutrophils, which secrete highly inflammatory proteins. Blocking IL-3 protected mice from sepsis-induced death.

Science, this issue p. 1260; see also p. 1201

Abstract

Sepsis is a frequently fatal condition characterized by an uncontrolled and harmful host reaction to microbial infection. Despite the prevalence and severity of sepsis, we lack a fundamental grasp of its pathophysiology. Here we report that the cytokine interleukin-3 (IL-3) potentiates inflammation in sepsis. Using a mouse model of abdominal sepsis, we showed that innate response activator B cells produce IL-3, which induces myelopoiesis of Ly-6Chigh monocytes and neutrophils and fuels a cytokine storm. IL-3 deficiency protects mice against sepsis. In humans with sepsis, high plasma IL-3 levels are associated with high mortality even after adjusting for prognostic indicators. This study deepens our understanding of immune activation, identifies IL-3 as an orchestrator of emergency myelopoiesis, and reveals a new therapeutic target for treating sepsis.

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