众所周知，放射治疗会导致患者的淋巴细胞减少，而这与负面结果相关。由于放射能同时具有免疫刺激和免疫抑制的效果，其机制尚不完全清楚。肿瘤剂量整形、剂量分数和选择性淋巴结照射在放射治疗中对淋巴细胞减少和免疫反应的影响是一个活跃的研究领域。此外，理解放射对免疫系统的影响对于设计和解释将放射与免疫检查点抑制剂结合的临床试验非常重要，包括放射剂量和治疗方案。虽然只有总淋巴细胞群体的几个百分点是循环的，但有推测它们的较高辐射敏感性可能对淋巴细胞减少起到贡献，甚至是主要原因。本综述总结了基于人类、小动物和体外研究的淋巴细胞辐射敏感性的已发表数据。数据表明，不同淋巴细胞亚群的辐射敏感性存在差异，影响它们的相对贡献和因此免疫反应的动态性。一般来说，B细胞似乎比T细胞更敏感，而NK细胞似乎是最抗性的。然而，已报道的剂量-反应数据表明，在患者的淋巴细胞减少情况下，除了细胞死亡之外，还必须考虑其他因素。辐射很可能不仅会影响绝对淋巴细胞计数，还可能会影响淋巴细胞的多样性和活性。综合回顾的数据表明，辐射引起的淋巴细胞凋亡不太可能是放射引起的淋巴细胞减少的唯一因素。Copyright © 2023 Paganetti.

It is well known that radiation therapy causes lymphopenia in patients and that this is correlated with a negative outcome. The mechanism is not well understood because radiation can have both immunostimulatory and immunosuppressive effects. How tumor dose conformation, dose fractionation, and selective lymph node irradiation in radiation therapy does affect lymphopenia and immune response is an active area of research. In addition, understanding the impact of radiation on the immune system is important for the design and interpretation of clinical trials combining radiation with immune checkpoint inhibitors, both in terms of radiation dose and treatment schedules. Although only a few percent of the total lymphocyte population are circulating, it has been speculated that their increased radiosensitivity may contribute to, or even be the primary cause of, lymphopenia. This review summarizes published data on lymphocyte radiosensitivity based on human, small animal, and in vitro studies. The data indicate differences in radiosensitivity among lymphocyte subpopulations that affect their relative contribution and thus the dynamics of the immune response. In general, B cells appear to be more radiosensitive than T cells and NK cells appear to be the most resistant. However, the reported dose-response data suggest that in the context of lymphopenia in patients, aspects other than cell death must also be considered. Not only absolute lymphocyte counts, but also lymphocyte diversity and activity are likely to be affected by radiation. Taken together, the reviewed data suggest that it is unlikely that radiation-induced cell death in lymphocytes is the sole factor in radiation-induced lymphopenia.Copyright © 2023 Paganetti.