This single-center, retrospective study aimed to explore the immune characteristics of COVID-19 and biomarkers to predict the severity of this disease. Patients infected with SARS-CoV-2 (n = 215) treated at the First Affiliated Hospital of Nanchang University from January 24 to March 12, 2020, were included in the study and classified into severe and non-severe groups. Peripheral immunocyte count and cytokine statuses were compared. The correlation between immune status, cytokine levels, and disease severity was analyzed. Leukocyte numbers were normal in both groups; however, they were relatively high (7.19 × 10⁹/L) in patients of the severe group. Leukocyte distributions differed between the two groups; the severe group had a higher percentage of neutrophils and lower percentage of lymphocytes compared with the non-severe group, and absolute lymphocyte numbers were below normal in both groups, and particularly deficient in patients in the severe group. Lymphocyte counts have negative correlation with duration of hospital period whereas neutrophil count has no significant correlation with it. Of tested cytokines, IL-6 levels were significantly higher in the severe group (P = 0.0418). Low level of lymphocyte predicts severity of COVID-19. IL-6 levels were significantly higher in the severe group, especially in some extremely severe patients. But we did not detect the significant correlation between severity of COVID-19 with IL-6 level which may be due to limited case numbers. Our observations encourage future research to understand the underlying molecular mechanisms and to improve treatment outcome of COVID-19.

这项单中心、回顾性研究旨在探索 COVID-19 的免疫特征和生物标志物，以预测这种疾病的严重程度。2020 年 1 月 24 日至 3 月 12 日在南昌大学第一附属医院接受治疗的SARS-CoV-2 感染患者（n  = 215）被纳入研究，并分为重症组和非重症组。比较外周免疫细胞计数和细胞因子状态。分析了免疫状态、细胞因子水平和疾病严重程度之间的相关性。两组白细胞数均正常；但是，它们相对较高（7.19 × 10 ⁹/L) 在重症组患者中。两组之间的白细胞分布不同；重症组中性粒细胞百分比高于非重症组，淋巴细胞百分比低于非重症组，两组绝对淋巴细胞数均低于正常值，重症组患者尤为明显。淋巴细胞计数与住院时间呈负相关，而中性粒细胞计数与住院时间无显着相关性。在测试的细胞因子中，重症组的 IL-6 水平显着升高（P = 0.0418)。淋巴细胞水平低可预测 COVID-19 的严重程度。重症组的IL-6水平显着升高，特别是在一些极严重的患者中。但我们没有发现 COVID-19 的严重程度与 IL-6 水平之间存在显着相关性，这可能是由于病例数有限。我们的观察结果鼓励未来的研究了解潜在的分子机制并改善 COVID-19 的治疗结果。