Subpopulation profile of blood leukocytes in assessing severity of COVID-19 and in conditions associated with cytokine storm

Currently, the clinical manifestations of COVID-19 patients are classified from mild to severe, especially in groups of patients susceptible to chronic diseases. Selection of the most informative prognostic indices of possible outcome or severe course of the disease in COVID-19 patients is required at early stage in order to determine effective treatment strategy. The earliest predictors of clinical deterioration in COVID-19 are elevated levels of interleukin-6, interleukin-10, C-reactive protein, procalcitonin, and other indices of innate immune system. The objectives of this study included a search for the most informative parameters of general clinical blood analysis and the main lymphocyte subpopulations in patients with COVID-19, which may be helpful in interpreting the severity of the disease and development of a cytokine storm, along with clinical manifestations and functional diagnostic methods. We conducted a retrospective cohort study of peripheral blood in 65 patients including 57 males and 8 females. The age of the patients ranged from 32 to 82 years (an average of 48.6 years old). After examining the total blood counts in 65 samples, cytometric analysis was performed using the Cytomics™ FC 500 series flow cytofluorometry system (Beckman Coulter, USA), with CD45-ECD, CD3-FITC, CD4-PC7, CD8-PE, CD19-PC-5, CD16 + 56-PE monoclonal antibodies from Beckman Coulter (USA). Statistical processing of the research results was carried out in the IBM SPSS Statistics 26.0 program (IBM, USA). In the group of patients with COVID-19, absolute lymphopenia is noted along with neutrophilia at the initial medical treatment, resulting into increased values of the neutrophil-leukocyte and leukocyte-T-lymphocyte indices. These indexes are quite informative and can be used in predicting disease risks. Determination of the most reliable indices of cellular immunity, such as CD3 + , CD3 + CD4 + , CD3 + CD8 + , CD3 - CD16 + CD56 + lymphocytes, in addition to a clinical blood test, may assess the features of the patients’ immune response to SARS-CoV-2 infection, helping to predict the disease severity, and make a decision to change the treatment strategy if required.