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

 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.

 We used flow cytometry to determine the relationship between disease severity, lymphocyte subsets distribution, and cytokine level alterations in COVID-19 patients.

 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.

 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-α (P = 0.004), IP-10 (P < 0.001), IFN-λ1 (IL-29) (P < 0.001), IFN-λ2/3 (IL-28A/B) (P = 0.011), IFN-β (P < 0.001), IL-10 (P < 0.001), and IFN-γ (P < 0.001) levels were statistically higher in patients than in the controls.

 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.