Possible Mechanisms of Lymphocyte Deficiency in COVID-19 Patients

Creative representation of SARS-CoV-2 particles (not to scale). Credits: National Institute of Infectious Diseases, NIH

Scientists at RUDN, the National Center for Hematology Research, and Lomonosov Moscow State University have discovered one of the possible pathogenic mechanisms of severe lymphopenia in patients with COVID-19. For the first time, they presented evidence of a possible direct infection of lymphocytes with SARS-CoV-2 virions.The article was published in the journal virus..

Lymphocytes are the major cells of the immune system. Deep lymphopenia (≤1000 / µl) is observed in 96% of patients with severe COVID-19 and 80% of patients with moderate COVID-19. The etiology of lymphopenia in patients with COVID-19 is not fully understood and consists of more than 10 possible mechanisms, extrapulmonary dissemination, and the direct effect of SARS-CoV-2 on lymphoid tissue. It has been.

“The purpose of this study was to assess the viral levels and patterns of SARS-Cov-2 dissemination into the lungs, medial lymph nodes, and spleen of patients with COVID-19-associated lymphopenia,” said Igor Babichenko. Says. Doctor of Medicine, Dean of the Department of Pathology and Anatomy, RUDN University.

Scientists have found comprehensive molecular genetic and immunohistochemicals of lung tissue, mediastinal lymph nodes lying along the path of lymphatic flow from the lungs, and the spleen of 36 patients who died of COVID-19. , And electron microscopy was performed. Lymphocytopenia was detected in 63.8% of them, and lymphocyte levels were below the critical value of 1 million cells per ml of blood.

In 33% of patients, the virus was detected in the lungs with an average viral load of 239.The cellular status of these patients is bronchopneumonia (acute inflammation of the bronchiolar wall) Acute respiratory distress syndrome (ARDS) Proliferative phase in which the lungs are recovering (although shortness of breath and other symptoms persist). In 58.4% of patients, SARS-CoV-2 was detected in the lungs, lymph nodes, and spleen, with a mean virus of 12,116 in the lungs, 832 in the lymph nodes, and 71.5 in the spleen. This corresponds to the exudative phase of ARDS, where gas exchange is interrupted when lung capillaries and alveoli are damaged. Immunohistochemical analysis showed the presence of the virus in lung macrophages, bronchiolic epithelial cells, and alveoli. During electron microscopy, for the first time, scientists found lymph with SARS-CoV-2 particles that could cause the development of lymphopenia due to massive lymphocyte apoptosis, previously described in the associated SARS-CoV. We have succeeded in proving the possibility of direct infection of lymphocytes. And MERS-CoV infection.

“Extrapulmonary dissemination of SARS-CoV-2 in lymphoid tissues occurs during the exudative phase of ARDS, which is associated with shorter stays in the ICU and increased SARS-CoV-2 virus loading. I have. lung Tissue compared to patients with SARS-CoV-2 dissemination confined to the lung.The discovery of lymphocytes infected with SARS-COV-2 particles, which we first revealed, may indicate that SARS-COV-2 can be induced. Lymphocytopenia Through the potential for direct cytotoxic effects. ” Doctor of Medicine, Dean of the Department of Pathology and Anatomy, People’s Friendship University of RUDN.

Studies reveal two stages of infection in patients with severe COVID-19 pneumonia

For more information:
Viral load and pattern of SARS-CoV-2 dissemination into the lungs, mediastinal lymph nodes, and spleen of patients with COVID-19-related lymphopenia, Adhamjon Abdullaev et al, virus (2021). DOI: 10.3390 / v13071410

Provided by Russian Basic Research Foundation

Quote: Https: // COVID-19 (2021, October 22) obtained on October 22, 2021 Possible Mechanisms of Patient Lymphocyte Deficiency

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Possible Mechanisms of Lymphocyte Deficiency in COVID-19 Patients

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