The main role of the human immune system is to eliminate cells presenting foreign antigens and abnormal patterns, while maintaining self-tolerance. However, when facing highly variable pathogens or antigens very similar to self-antigens, this system can fail in completely eliminating the anomalies, leading to the establishment of chronic pathologies. Prototypical examples of immune system defeat are cancer and Human Immunodeficiency Virus-1 (HIV-1) infection. In both conditions, the immune system is persistently exposed to antigens leading to systemic inflammation, lack of generation of long-term memory and exhaustion of effector cells. This triggers a negative feedback loop where effector cells are unable to resolve the pathology and cannot be replaced due to the lack of a pool of undifferentiated, self-renewing memory T cells. In addition, in an attempt to reduce tissue damage due to chronic inflammation, antigen presenting cells and myeloid components of the immune system activate systemic regulatory and tolerogenic programs. Beside these homologies shared between cancer and HIV-1 infection, the immune system can be shaped differently depending on the type and distribution of the eliciting antigens with ultimate consequences at the phenotypic and functional level of immune exhaustion. T cell differentiation, functionality, cytotoxic potential and proliferation reserve, immune-cell polarization, upregulation of negative regulators (immune checkpoint molecules) are indeed directly linked to the quantitative and qualitative differences in priming and recalling conditions. Better understanding of distinct mechanisms and functional consequences underlying disease-specific immune cell dysfunction will contribute to further improve and personalize immunotherapy. In the present review, we describe relevant players of immune cell exhaustion in cancer and HIV-1 infection, and enumerate the best-defined hallmarks of T cell dysfunction. Moreover, we highlight shared and divergent aspects of T cell exhaustion and T cell activation to the best of current knowledge.

人类免疫系统的主要作用是消除呈现外来抗原和异常模式的细胞，同时保持自我耐受。但是，当面对高度可变的病原体或与自身抗原非常相似的抗原时，该系统可能无法完全消除异常，导致建立慢性病理。免疫系统衰竭的典型例子是癌症和人类免疫缺陷病毒-1（HIV-1）感染。在这两种情况下，免疫系统都持续暴露于导致全身性炎症，缺乏长期记忆力产生和效应细胞衰竭的抗原。这会触发一个负反馈回路，在该回路中，由于缺乏未分化的，自我更新的记忆T细胞池，效应细胞无法解决病理问题并且无法被替换。此外，为了减少由于慢性炎症引起的组织损伤，抗原呈递细胞和免疫系统的髓样成分激活了系统性调节和致耐受性程序。除了在癌症和HIV-1感染之间共享的这些同源性之外，免疫系统的形状也可能不同，具体取决于引发抗原的类型和分布，最终影响免疫力衰竭的表型和功能水平。实际上，T细胞的分化，功能，细胞毒性潜能和增殖储备，免疫细胞极化，负调节剂（免疫检查点分子）的上调与引发和召回条件的数量和质量上的差异直接相关。更好地了解疾病特异性免疫细胞功能障碍的不同机制和功能后果将有助于进一步改善免疫疗法并使其个性化。在本综述中，我们描述了癌症和HIV-1感染中免疫细胞衰竭的相关因素，并列举了T细胞功能障碍的最佳定义。此外，根据目前的知识，我们重点介绍了T细胞衰竭和T细胞活化的共同和不同方面。