Clinical indicators and immunological characteristics of COVID-19: a retrospective analysis of 123 cases

To study the relevant clinical indicators and immunological characteristics of patients with different levels of Corona Virus Disease 2019（COVID-19）.

A total of 123 patients with confirmed COVID-19 admitted to Wuhan Huoshenshan Hospital from February 5 to April 10, 2020 were enrolled as the study objects. According to Novel Coronavirus Pneumonia Treatment Protocol（6th Edition）, they were divided into recovery（n=69）, severe（n=45）, and death（n=9）groups. Their electronic medical records were collected, and basic data, clinical symptoms, and results of laboratory examinations were analyzed statistically. A cross-sectional study was conducted on the expression levels of serum cytokines, T cell characteristics, and PD-1 expression on T cells. All data were analyzed using GraphPad Prism 8.0 software.

There were 74 male and 49 female COVID-19 patients, with a median age of 63.94 years in this study, and among them, 79 were over 60 years old. Plasma C-reactive protein（CRP）, lactate dehydrogenase（LDH）, hydroxybutyrate dehydrogenase（HBHD）, cystatin C（CysC）, and procalcitonin（PCT）were significantly elevated in the severe disease and death groups（P<0.05）. The 2 groups also had obviously higher serum levels of IL-2, IL-6, IL-8, IL-10 and IL-17 than the recovery group（P<0.05）. The patients from the death group had the lowest peripheral blood lymphocyte count and the highest neutrophil count（P<0.05）. The expression level of PD-1 in CD4⁺ T cells and CD8⁺ T cells was notably higher in the severe and death groups than the recovery group（P<0.05）.

Age is associated with the level of COVID-19. And the levels of cytokines such as IL-6 and IL-8, decrease of T lymphocytes and exhaustion of T cell function are closely correlated with the severity of COVID-19.