Immunosuppression as a Hallmark of Critical COVID-19: Prospective Study

• Main Authors: Elżbieta Kalicińska, Donata Szymczak, Aleksander Zińczuk, Barbara Adamik, Jakub Smiechowicz, Tomasz Skalec, Danuta Nowicka-Suszko, Monika Biernat, Aleksandra Bogucka-Fedorczuk, Justyna Rybka, Adrian Martuszewski, Waldemar Gozdzik, Krzysztof Simon, Tomasz Wróbel
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Cells
• Subjects: immunosuppression; lymphocyte subsets; T cells; regulatory T cells; NK cells; TCR γ/δ cells
• Online Access: https://www.mdpi.com/2073-4409/10/6/1293

The dysregulation of both the innate and adaptive responses to SARS-CoV-2 have an impact on the course of COVID-19, and play a role in the clinical outcome of the disease. Here, we performed a comprehensive analysis of peripheral blood lymphocyte subpopulations in 82 patients with COVID-19, including 31 patients with a critical course of the disease. In COVID-19 patients who required hospitalization we analyzed T cell subsets, including Treg cells, as well as TCRα/β and γ/δ, NK cells, and B cells, during the first two weeks after admission to hospital due to the SARS-CoV-2 infection, with marked reductions in leukocytes subpopulations, especially in critically ill COVID-19 patients. We showed decreased levels of Th, Ts cells, Treg cells (both naïve and induced), TCRα/β and γ/δ cells, as well as CD16+CD56+NK cells in ICU compared to non-ICU COVID-19 patients. We observed impaired function of T and NK cells in critically ill COVID-19 patients with extremely low levels of secreted cytokines. We found that the IL-2/INFγ ratio was the strongest indicator of a critical course of COVID-19, and was associated with fatal outcomes. Our findings showed markedly impaired innate and adaptive responses in critically ill COVID-19 patients, and suggest that the immunosuppressive state in the case of a critical course of SARS-CoV-2 infection might reflect subsequent clinical deterioration and predict a fatal outcome.