Clinical symptoms of COVID-19 include fever, cough, and fatigue which may progress to acute respiratory distress syndrome (ARDS). The main hematological laboratory findings associated with the severe form of disease are represented by lymphopenia and eosinopenia which mostly occur in the elderly population characterized by cardiovascular comorbidities and immunosenescence. Besides, increased levels of D-dimer, procalcitonin, and C reactive protein (CRP) seem to be powerful prognostic biomarkers helping to predict the onset of coagulopathy. The host immune response to SARS-CoV-2 can lead to an aberrant inflammatory response or “cytokine storm” which contributes to the severity of illness. At immunological level, patients affected by a severe form of COVID-19 show poor clinical trajectories characterized by differential “immunotypes” for which T cell response seems to play a critical role in understanding pathogenic mechanisms of disease. Also, patients with mild to severe COVID-19 displayed macrophage activation syndrome (MAS), very low human leukocyte antigen D related (HLA-DR) expression with a parallel reduction of CD04⁺ lymphocytes, CD19 lymphocytes, and natural killer (NK) cells. Corticosteroids resulted the best therapy for the immune dysregulation whereas repurposing of tocilizumab (IL-6 receptor antagonist) appears to have mixed results in patients with COVID-19. Besides, anticoagulative therapy was associated with reduced in-hospital mortality and need of intubation among COVID-19 patients. Furthermore, the beneficial use of intravenous immunoglobulin (IVIG) and passive immunotherapy with convalescent plasma needs to be validated in large controlled clinical trials. In this review, we summarize the main hematological parameters with a prognostic value in COVID-19 and the basis of immunological reactivity during COVID-19, with a focus on ongoing clinical trials evaluating immune targets as possible therapeutic strategies.

COVID-19 的临床症状包括发烧、咳嗽和疲劳，可能会发展为急性呼吸窘迫综合征 (ARDS)。与严重疾病相关的主要血液学实验室检查结果以淋巴细胞减少和嗜酸性粒细胞减少为代表，其主要发生在以心血管合并症和免疫衰老为特征的老年人群中。此外，D-二聚体、降钙素原和 C 反应蛋白 (CRP) 水平升高似乎是强有力的预后生物标志物，有助于预测凝血病的发生。宿主对 SARS-CoV-2 的免疫反应可能导致异常炎症反应或“细胞因子风暴”，从而加剧疾病的严重性。在免疫学水平上，受严重形式的 COVID-19 影响的患者表现出较差的临床轨迹，其特征是不同的“免疫类型”，其中 T 细胞反应似乎在理解疾病的致病机制中发挥着关键作用。此外，轻度至重度 COVID-19 患者表现出巨噬细胞激活综合征 (MAS)、人类白细胞抗原 D 相关 (HLA-DR) 表达极低，同时 CD04 ⁺淋巴细胞、CD19 淋巴细胞和自然杀伤 (NK) 细胞同时减少。皮质类固醇是治疗免疫失调的最佳疗法，而托珠单抗（IL-6 受体拮抗剂）的重新利用似乎对 COVID-19 患者产生了好坏参半的结果。此外，抗凝治疗与减少 COVID-19 患者的住院死亡率和插管需求有关。此外，静脉注射免疫球蛋白（IVIG）和恢复期血浆被动免疫疗法的有益用途需要在大型对照临床试验中得到验证。 在这篇综述中，我们总结了对 COVID-19 具有预后价值的主要血液学参数以及 COVID-19 期间免疫反应性的基础，重点是评估免疫靶点作为可能的治疗策略的正在进行的临床试验。