Macrophages are innate immune cells with well-established roles in the primary response to pathogens, but also in tissue homeostasis, coordination of the adaptive immune response, inflammation, resolution, and repair. These cells recognize danger signals through receptors capable of inducing specialized activation programs. The classically known macrophage activation is induced by IFN-gamma, which triggers a harsh proinflammatory response that is required to kill intracellular pathogens. Macrophages also undergo alternative activation by IL-4 and IL-13, which trigger a different phenotype that is important for the immune response to parasites. Here we review the cellular sources of these cytokines, receptor signaling pathways, and induced markers and gene signatures. We draw attention to discrepancies found between mouse and human models of alternative activation. The evidence for in vivo alternative activation of macrophages is also analyzed, with nematode infection as prototypic disease. Finally, we revisit the concept of macrophage activation in the context of the immune response.

中文翻译：

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巨噬细胞的替代激活：免疫功能观点。

巨噬细胞是先天免疫细胞，在对病原体的初级反应以及组织稳态、适应性免疫反应的协调、炎症、消退和修复中发挥着公认的作用。这些细胞通过能够诱导特殊激活程序的受体识别危险信号。经典已知的巨噬细胞激活是由 IFN-γ 诱导的，它会触发一种苛刻的促炎反应，这是杀死细胞内病原体所需的。巨噬细胞也会被 IL-4 和 IL-13 选择性激活，这会触发不同的表型，这对寄生虫的免疫反应很重要。在这里，我们回顾了这些细胞因子的细胞来源、受体信号通路以及诱导标记和基因特征。我们提请注意小鼠和人类替代激活模型之间的差异。还分析了巨噬细胞在体内替代激活的证据，线虫感染是原型疾病。最后，我们在免疫反应的背景下重新审视巨噬细胞激活的概念。