Analysis of Immune Profiles Related to Disease Severity in COVID-19 by Flow Cytometry

Background: More than 768 million people have been affected by COVID-19. Identifying lymphocyte subsets and cytokine level abnormalities in COVID-19 patients is essential to gain new insights and data on immunity mechanisms against viral infections. Objectives: We used flow cytometry to determine the relationship between disease severity, lymphocyte subsets distribution, and cytokine level alterations in COVID-19 patients. Methods: Totally 94 COVID-19 patients (32 mild, 31 moderate, and 31 severe) and 27 healthy individuals were included in the cross-sectional study. The distribution of peripheral lymphocyte subsets and cytokine levels was assessed by flow cytometry. Results: The percentages of CD56(+) natural killer (NK) cells in all patient groups and total T lymphocytes in moderate and severe groups were significantly lower than those in the control group (P < 0.001). Also, IL-2 (P < 0.001), IL-17A (P < 0.001), IL-4 (P < 0.001), IL-6 (P < 0.001), TNF-alpha (P = 0.004), IP-10 (P < 0.001), IFN-lambda 1 (IL-29) (P < 0.001), IFN-lambda 2/3 (IL-28A/B) (P = 0.011), IFN-beta (P < 0.001), IL-10 (P < 0.001), and IFN-gamma (P < 0.001) levels were statistically higher in patients than in the controls. Conclusions: Our data revealed that increased levels of certain cytokines in peripheral blood contribute to disease severity. Increased CRP (OR: 1.012, %95 CI: 1.002 - 1.023, P = 0.038) and IL-10 (OR: 1.068, %95 CI: 1.000 - 1.141, P = 0.049) levels, decreased CD56(+) NK percentage (OR: 0.576, %95 CI: 0.376 - 0.882, P = 0.011) and lymphocyte count (OR: 0.02, %95 CI: 0.001 - 0.368, P = 0.009), and the presence of diabetes mellitus and mechanical ventilation were independent predictors of mortality.