The adaptive immune system is essential for host defense against pathogenic challenges, and a major constituent is the CD8+ cytotoxic T cell. Ordinarily, CD8+ T cells are endowed with a unique ability to specifically recognize and destroy their targets. However, in cases where disease emerges, especially in cancer, the efficacy of the CD8+ T cell response is frequently counterbalanced in a 'tug-of-war' by networks of tumor-driven mechanisms of immune suppression. As a result, antitumor CD8+ T cell activity is hampered, which contributes to clinical manifestations of disease. It is now well-recognized that prominent elements of that network include myeloid-derived suppressor cells (MDSC) and macrophages which assume tumor-supportive phenotypes. Both myeloid populations are thought to arise as consequences of chronic inflammatory cues produced during the neoplastic process. Numerous preclinical studies have now shown that inhibiting the production, trafficking and/or function of these immune suppressive myeloid populations restore antitumor CD8+ T cell responses during both immune surveillance or in response to immune-targeted interventions. Correlative studies in cancer patients support these preclinical findings and, thus, have laid the foundation for ongoing clinical trials in patients receiving novel agents that target such myeloid elements alone or in combination with immunotherapy to potentially improve cancer patient outcomes. Accordingly, this review focuses on how and why it is important to study the myeloid-T cell interplay as an innovative strategy to boost or reinvigorate the CD8+ T cell response as a critical weapon in the battle against malignancy.

中文翻译：

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髓细胞驱动的机制成为抗肿瘤CD8 + T细胞活性的障碍。

适应性免疫系统对于宿主防御病原体攻击至关重要，其主要成分是CD8 +细胞毒性T细胞。通常，CD8 + T细胞具有独特的能力来特异性识别和破坏其靶标。但是，在疾病出现的情况下，尤其是在癌症中，CD8 + T细胞反应的功效在“拔河比赛”中经常被肿瘤驱动的免疫抑制机制网络抵消。结果，抗肿瘤CD8 + T细胞活性受到阻碍，这有助于疾病的临床表现。现在已经众所周知，该网络的重要组成部分包括髓样来源的抑制细胞（MDSC）和假定肿瘤支持表型的巨噬细胞。人们认为这两种髓细胞种群都是在肿瘤形成过程中产生的慢性炎症提示的结果。现在，许多临床前研究表明，抑制这些免疫抑制性髓细胞群体的产生，运输和/或功能可在免疫监视期间或针对免疫靶向干预的过程中恢复抗肿瘤CD8 + T细胞反应。在癌症患者中进行的相关研究支持了这些临床前研究结果，因此为接受单独靶向此类髓样物质或与免疫疗法结合以潜在改善癌症患者预后的新型药物的患者的正在进行的临床试验奠定了基础。因此，