IFN-γ, a proinflammatory cytokine produced primarily by T cells and NK cells, activates macrophages and engages mechanisms to control pathogens. Although there is evidence of IFN-γ production by murine macrophages, IFN-γ production by normal human macrophages and their subsets remains unknown. Herein, we show that human M1 macrophages generated by IFN-γ and IL-12– and IL-18–stimulated monocyte-derived macrophages (M0) produce significant levels of IFN-γ. Further stimulation of IL-12/IL-18–primed macrophages or M1 macrophages with agonists for TLR-2, TLR-3, or TLR-4 significantly enhanced IFN-γ production in contrast to the similarly stimulated M0, M2a, M2b, and M2c macrophages. Similarly, M1 macrophages generated from COVID-19–infected patients’ macrophages produced IFN-γ that was enhanced following LPS stimulation. The inhibition of M1 differentiation by Jak inhibitors reversed LPS-induced IFN-γ production, suggesting that differentiation with IFN-γ plays a key role in IFN-γ induction. We subsequently investigated the signaling pathway(s) responsible for TLR-4–induced IFN-γ production in M1 macrophages. Our results show that TLR-4–induced IFN-γ production is regulated by the ribosomal protein S6 kinase (p70S6K) through the activation of PI3K, the mammalian target of rapamycin complex 1/2 (mTORC1/2), and the JNK MAPK pathways. These results suggest that M1-derived IFN-γ may play a key role in inflammation that may be augmented following bacterial/viral infections. Moreover, blocking the mTORC1/2, PI3K, and JNK MAPKs in macrophages may be of potential translational significance in preventing macrophage-mediated inflammatory diseases.

IFN-γ 是一种主要由 T 细胞和 NK 细胞产生的促炎细胞因子，可激活巨噬细胞并参与控制病原体的机制。尽管有证据表明鼠巨噬细胞产生 IFN-γ，但正常人巨噬细胞及其亚群产生的 IFN-γ 仍然未知。在此，我们显示由 IFN-γ 和 IL-12 和 IL-18 刺激的单核细胞衍生的巨噬细胞 (M0) 产生的人类 M1 巨噬细胞产生显着水平的 IFN-γ。与类似刺激的 M0、M2a、M2b 和 TLR-2、TLR-3 或 TLR-4 激动剂进一步刺激 IL-12/IL-18 引发的巨噬细胞或 M1 巨噬细胞显着增强了 IFN-γ 的产生。 M2c 巨噬细胞。同样，由感染 COVID-19 的患者的巨噬细胞产生的 M1 巨噬细胞产生 IFN-γ，在 LPS 刺激后增强。Jak 抑制剂对 M1 分化的抑制逆转了 LPS 诱导的 IFN-γ 产生，表明 IFN-γ 分化在 IFN-γ 诱导中起关键作用。我们随后研究了负责 M1 巨噬细胞中 TLR-4 诱导的 IFN-γ 产生的信号通路。我们的结果表明，TLR-4 诱导的 IFN-γ 产生受核糖体蛋白 S6 激酶（p70S6K）通过激活 PI3K、哺乳动物雷帕霉素复合物 1/2（mTORC1/2）的靶标和 JNK MAPK 通路调节. 这些结果表明 M1 衍生的 IFN-γ 可能在炎症中起关键作用，炎症可能在细菌/病毒感染后加剧。此外，阻断巨噬细胞中的 mTORC1/2、PI3K 和 JNK MAPKs 可能在预防巨噬细胞介导的炎症性疾病方面具有潜在的转化意义。