Character of inflammatory response in pulmonary parenchyma of patients with different clinical courses of COVID-19

COVID-19 presents with a wide range of symptoms and is classified as an infectious disease in which an excessive inflammatory response is the main cause of poor clinical outcome. Further research into the issues of pathogenesis, morphogenesis, especially features of the inflammatory response during infection caused by the SARS-CoV-2 virus is promising. The aim of this study was to evaluate the relationship between histological changes in the lung parenchyma of patients and the severity of clinical manifestations of COVID-19. The object of the study was lung tissue from patients with verified new coronavirus infection SARS-CoV-2 using PCR testing and hospital records of patients. Immunohistochemical analysis with CD8 and CD4 antibodies was performed to identify cytotoxic and helper T lymphocytes in lung tissue. The expression of IL-6 as one of the main mediators of the cytokine storm was studied. It was found that in the lung parenchyma of patients infected with the new strain of coronavirus SARS-CoV-2, atypical expression of CD4 and CD8 markers was detected in the cytoplasm of alveolar macrophages and desquamated type II pneumocytes. With the development of a cytokine storm in patients infected with the SARS-CoV-2 virus, a mechanism for the formation of early interstitial pulmonary fibrosis is triggered, the severity of which depends on the clinical and laboratory parameters of the cytokine storm.