PI3Kγ通路在结核病中维持免疫耗竭的作用机制

Some inhibitory receptors upregulated in T cells when active tuberculosis occurred which was associated with T cells exhaustion, while the mechanism was not yet elucidated. Our previous study indicated that PD-1 and its ligand PD-L increased in T cells and Macrophages in active tuberculosis and decreased after efficient anti-TB therapy. The phagocytosis and clearance of Macrophages with BCG, as well as T cells proliferation was significantly augmented when blocking PD-1/PD-L interaction with specific antibodies. The mechanism of PD-L upregulation in Macrophages needed to be further investigated. Recently, studies showed that PI3Kγ was a molecular switch that controlled immune suppression. PI3Kγ pathway could have some effects on PD-L1 expression in Macrophages. We also found that using PI3Kγ inhibitor could significantly augment the cytokine IFN-γ level of T cells in tuberculosis. Therefore, we hypothesized that PI3Kγ pathway in Macrophages could maintain T cells exhaustion in tuberculosis. We planned to use flow cytometry, protein immunoblotting, plasmid transfection and small RNA interference to elucidate the regulation of PI3Kγ in Macrophages on PD-L expression and involved signaling pathway. These findings would be expected to shed light on the development of new immune checkpoint targeting PI3Kγ in tuberculosis.

T细胞功能耗竭在活动性结核的发病中起了重要作用。耗竭的T细胞表达PD-1等多种共抑制分子。我们前期研究发现PD-1及其配体PD-L的表达在活动性结核患者中上升，抗结核治疗后下降。阻断PD-1通路可以部分恢复巨噬细胞和T细胞的功能。新近关于肿瘤的研究确定了PI3Kγ是控制巨噬细胞免疫抑制的重要分子开关，PI3Kγ能介导PD-L的表达。我们也发现阻断PI3Kγ可以恢复结核病人的T细胞功能。因此，我们推测在结核病中巨噬细胞通过PI3Kγ通路上调PD-L的表达而影响巨噬细胞的功能，同时增强PD-1介导的T细胞功能抑制。本课题拟采用免疫学和细胞生物学等技术方法来研究活动性结核感染中PI3Kγ通路调节巨噬细胞中PD-L的表达对巨噬细胞功能和T细胞功能的影响，以及相关分子机制，从而明确PI3Kγ通路与结核菌逃逸宿主免疫清除和免疫控制的关系，为提出新的免疫治疗靶点奠定基础。

我们前期研究发现PD-1及其配体PD-L的表达在活动性结核患者中上升，抗结核治疗后下降。阻断PD-1通路可以部分恢复巨噬细胞和T细胞的功能。在肿瘤的研究中确定了PI3Kγ是控制巨噬细胞免疫抑制的重要分子开关，PI3Kγ能介导PD-L的表达。我们的研究发现结核患者外周血单核细胞中的PI3Kγ表达在使用BCG刺激后明显增强，阻断PI3Kγ可以恢复结核病人T细胞功能，使用质粒敲减或者慢病毒过表达PI3Kγ后，单核细胞的吞噬杀菌能力还在进一步研究。因此，我们推测在结核病中巨噬细胞通过PI3Kγ通路上调PD-L的表达而影响巨噬细胞的功能，同时增强PD-1介导的T细胞功能抑制。本课题采用免疫学和细胞生物学等技术方法来研究活动性结核感染中PI3Kγ通路调节巨噬细胞中PD-L的表达对巨噬细胞功能和T细胞功能的影响，以及相关分子机制，从而明确PI3Kγ通路与结核菌逃逸宿主免疫清除和免疫控制的关系，为提出新的免疫治疗靶点奠定基础。