Analysis of Lymphocyte Subpopulations and Cytokines in COVID-19-Associated Pneumonia and Community-Acquired Pneumonia

Background The 2019 novel coronavirus SARS-CoV-2 caused large outbreaks of COVID-19 worldwide. COVID-19 resembles community-acquired pneumonia (CAP). Our aim was to identify lymphocyte subpopulations to distinguish between COVID-19 and CAP.Methods We compared the peripheral blood lymphocytes and their subsets in 296 patients with COVID-19 and 130 patients with CAP. Parameters for independent prediction of COVID-19 were calculated by logistic regression.Results The main lymphocyte subpopulations (CD3 + CD4 + , CD16 + CD56 + , and CD4 + /CD8 + ratio) and cytokines (TNF- α and IFN- γ ) of COVID-19 patients were significantly different from that of CAP patients. CD16 + CD56 + %, CD4 + /CD8 + ratio, CD19 + , and CD3 + CD4 + were identified as predictors of COVID-19 diagnosis by logistic regression. In addition, the CD3 + CD4 + counts, CD3 + CD8 + counts, andTNF- α are independent predictors of disease severity in patients.Conclusions Lymphopenia is an important part of SARS-CoV-2 infection, and lymphocyte subsets and cytokines may be useful to predict the severity and clinical outcomes of the disease.