Abstract
BackgroundBoth COVID-19 and influenza A contribute to increased mortality among the elderly and those with existing comorbidities. Changes in the underlying immune mechanisms determine patient prognosis. This study aimed to analyze the role of lymphocyte subsets in the immunopathogenesisof COVID-19 and severe influenza A, and examined the clinical significance of their alterations in the prognosis and recovery duration.MethodsBy retrospectively reviewing of patients in four groups (healthy controls, severe influenza A, non-severe COVID-19 and severe COVID-19) who were admitted to Ditan hospital between 2018 to 2020, we performed flow cytometric analysis and compared the absolute counts of leukocytes, lymphocytes, and lymphocyte subsets of the patients at different time points (weeks 1–4).ResultsWe reviewed the patients’ data of 94 healthy blood donors, 80 Non-severe-COVID-19, 19 Severe-COVID-19 and 37 severe influenza A. We found total lymphocytes (0.81 × 109/L vs 1.74 × 109/L, P = 0.001; 0.87 × 109/L vs 1.74 × 109/L, P < 0.0001, respectively) and lymphocyte subsets (T cells, CD4+ and CD8+ T cell subsets) of severe COVID-19 and severe influenza A patients to be significantly lower than those of healthy donors at early infection stages. Further, significant dynamic variations were observed at different time points (weeks 1–4).ConclusionsOur study suggests the plausible role of lymphocyte subsets in disease progression, which in turn affects prognosis and recovery duration in patients with severe COVID-19 and influenza A.
Highlights
Both COVID-19 and influenza A contribute to increased mortality among the elderly and those with existing comorbidities
Our study suggests the plausible role of lymphocyte subsets in disease progression, which in turn affects prognosis and recovery duration in patients with severe COVID-19 and influenza A
As previous studies demonstrated that infection of humans with influenza A virus leads to an induction of apoptosis of a portion of CD3+, CD4+, CD8+, and CD19+ lymphocytes, resulting in a severe transient leukopenia, and that lymphocyte apoptosis, which represents a part of an overall beneficial immune response could be a possible mechanism of disease pathogenesis [4, 5]
Summary
Both COVID-19 and influenza A contribute to increased mortality among the elderly and those with existing comorbidities. The clinical manifestations of COVID-19 can be mild or severe, which the incidence of mortality is higher among the elderly and among those with preexisting comorbidities, including hypertension, cardiovascular and cerebrovascular disease, and diabetes, similar to influenza [1]. Their modes of transmission are by contact, droplets, or fomites [2, 3]. In view of the above, in this retrospective study, we analyzed the role of lymphocytes and lymphocyte subsets in the immunopathogenesis of COVID-19 and severe influenza A, to provide us with valuable insights for better understanding of the underlying immune mechanisms following SARS-Cov-2 and severe influenza A infections
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