Korean J Intern Med.  2022 Jan;37(1):201-209. 10.3904/kjim.2021.093.

Eosinophil-mediated lung inflammation associated with elevated natural killer T cell response in COVID-19 patients

• Kim DM
• Seo JW
• Kim Y
• Park U
• Ha NY
• Park H
• Yun NR
• Kim DY
• Yoon SH
• Na YS
• Moon DS
• Lim SC
• Kim CM
• Kim YS
• Cho NH

• KMID: 2524255
• DOI: http://doi.org/10.3904/kjim.2021.093

Abstract

Background/Aims
Coronavirus disease 2019 (COVID-19) is associated with acute respiratory syndrome. The mechanisms underlying the different degrees of pneumonia severity in patients with COVID-19 remain elusive. This study provides evidence that COVID-19 is associated with eosinophil-mediated inflammation.
Methods
We performed a retrospective case series of three patients with laboratory and radiologically confirmed COVID-19 pneumonia admitted to Chosun University Hospital. Demographic and clinical data on inflammatory cell lung infiltration and cytokine levels in patients with COVID-19 were collected.
Results
Cytological analysis of sputum, tracheal aspirates, and bronchoalveolar lavage fluid (BALF) samples from all three patients revealed massive infiltration of polymorphonuclear cells (PMNs), such as eosinophils and neutrophils. All sputum and BALF specimens contained high levels of eosinophil cationic proteins. The infiltration of PMNs into the lungs, together with elevated levels of natural killer T (NKT) cells in BALF and peripheral blood samples from patients with severe pneumonia in the acute phase was confirmed by flow cytometry.
Conclusions
These results suggest that the lungs of COVID-19 patients can exhibit eosinophil-mediated inflammation, together with an elevated NKT cell response, which is associated with COVID-19 pneumonia.

Keyword

COVID-19; SARS-CoV-2; Eosinophil; Natural killer T-cells; Bronchoalveolar lavage