Phagocytic activity of leukocytes in patients with COVID-19

The initial efforts to describe the inflammatory mechanisms associated with SARS-CoV-2 have revealed upregulation of circulating proinflammatory cytokines as well as activation of innate immune cells. The aim of the study was to investigate the phagocytic activity of leukocytes in hospitalized patients with COVID-19 (COronaVIrus Disease 2019). Methods. The phagocytic activity of leukocytes was studied in admitted patients with COVID-associated lung disease (n = 105). The mean age of the studied patients was 43.5 (37; 51) years; 69 for men, and 36 for women; the mean duration of the disease before hospitalization was 6 (4; 8) days. Using cluster analysis, two groups of patients (clusters) were formed according to the severity of COVID-19: Group 1 with the moderate course (n = 34) and Group 2 with the mild course (n = 71). Flow cytofluorimetry with determination of neutrophil (NI) and monocyte index (MI) was used to determine the phagocytic activity of neutrophils and monocytes in the peripheral blood. Results. The median NI in the studied patients was 97.9% (96.3; 99); the mean median MI was 91.2% (84.6; 95). The correlation analysis revealed statistically significant direct correlation of MI with SpO2 level (r = 0.21; 95% CI: 0.005 – 0.39; p = 0.04); inverse correlation of MI with CRP level (r = –0.31; 95% CI: –0.11 to –0.48; p = 0.003) and degree of lung damage by CT (r = –0.2; 95% CI: –0.11 to –0.48); p = 0.05). MI in the group with moderate course was statistically significantly lower than in the group with mild course of COVID-19 (86.7 (81.4; 91.7) and 92.6 (86.5; 95.4), p = 0.01). The blood MI of the initially more severe patients statistically significantly increased. Conclusion . Complicated forms of SARS-CoV-2 infection lead to a decrease in phagocytic activity of the monocytic-macrophage link of innate immunity. The degree of decrease in monocyte phagocytic activity is directly related to the severity of COVID-19, and the MI is comparable in the patients with severe and mild course after 30 days of treatment.