Alterations of blood Immune cells in elderly patients with COVID-19 and with or without pre-existing type 2 diabetes

Abstract

Elderly individuals, especially those with pre-existing conditions like type 2 diabetes mellitus (T2DM), have a high risk for developing severe cases of COVID-19. The aim of this work was to characterize the alterations of blood immune cells (BIC) in patients with symptomatic COVID-19 and confirmed SARS-CoV-2 infection, ≥60 years and who needed hospitalization in the Centro de Salud Hospital of Tucuman, Argentina, during the second peak of the pandemic in Argentina. Ten patients were enrolled from December 2020 to May 2021. Blood samples were taken at the time of admission (day 0) and five days after (day 5) for routine laboratory tests and the characteriza-tion of BIC by flow cytometry. Most of the patients were men (70%) aged between 60 and 78 years. The 70% of patients had T2DM while 50% had arterial hypertension. At day 0, all the patients had increased neutrophils and inflammatory markers (C reac-tive protein and D-dimers) and reduced numbers of lymphocytes, HLA-DRhi mono-cytes, CD16+CD56+ NK cells, CD3+HLA-DR+CD25+ cells, CD4+ and CD8+ T cells in blood. Patients received a standard treatment for COVID-19 care (O2, corticosteroids and antibiotics). The hospital treatment normalized the levels of BIC (day 5) in 30% of patients who were those with no comorbidities. In patients with T2DM, BIC recov-ery was variable. In T2DM patients who required administration of plasma (30%), prolonged O2 therapy (40%) or referral to the intensive care unit (10%) significant re-ductions of CD16+CD56+, CD3+HLA-DR+CD25+, CD4+ and CD8+ cells were observed between days 0 and 5. In line with previous studies, our results shows that absolute counts of major lymphocyte subsets in blood are significantly and substantially de-creased during the course of severe COVID-19 disease in elderly patients. These BIC alterations may persist despite clinical care in elderly patients with T2DM. Further studies are needed to investigate the utility of early lymphocyte subset measurements as prognostic biomarkers of disease severity, mortality, and response to treatment in COVID-19 elderly patients with T2DM.