Lymphocyte apoptosis in patients with coronavirus infection COVID-19

BACKGROUND: Lymphopenia in patients with coronavirus infection COVID-19 is associated with the risk of developing severe forms and unfavorable outcome. One of the reasons for the development of lymphopenia is apoptosis. AIM: Evaluation of the severity of peripheral blood lymphocytes' apoptosis in patients with moderate and severe COVID-19. MATERIAL AND METHODS: A total of 42 patients with COVID-19 aged 37 to 90 years were examined. They were hospitalized at the Republican Clinical Infectious Diseases Hospital named after Professor A.F. Agafonov, Kazan, from October 24, 2021 to March 1, 2022. In 13 patients, the lung lesion volume ranged from 10 to 25% (CT-1), in 20 — from 25 to 50% (CT-2), in 9 — from 50 to 75% (CT-3). Ribonucleic acid of the SARS-CoV-2 virus was isolated from the nasopharynx in 35 (83%) patients. COVID-19 was moderate in 14 patients, and severe in 28 patients. The control group consisted of 10 conditionally healthy people of the same age. Lymphocyte apoptosis was assessed by quantifying hypodiploid cells by changing the intensity of their staining with propidium iodide using flow cytometry. To determine the reliability of differences in indicators between the compared groups, the Mann–Whitney U-test was used, and when comparing percentages, the χ2 criterion was used. The reliability of differences was established at p 0.05. RESULTS: It was found that patients with COVID-19 had significantly higher lymphocyte apoptosis activity compared to the control group. The median of the studied indicator in patients with COVID-19 was 39.3%, while in the control group it was 15.1% (p 0.001). The severity of lymphocyte apoptosis correlated with the severity of the disease: the highest rates were recorded in patients with severe COVID-19 (p=0.02). Moreover, lymphocyte apoptosis 55% was associated with the risk of death (p=0.03). A moderate correlation was established between lymphocyte apoptosis rates and blood ferritin levels (Spearman coefficient p=0.39, p 0.05). CONCLUSION: Coronavirus infection COVID-19 was accompanied by an increase in the activity of peripheral blood lymphocyte apoptosis; the highest apoptosis rates were recorded in patients with severe COVID-19.