BACKGROUND: Since December 2019, novel coronavirus (SARS-CoV-2)-infected pneumonia (COVID-19) occurred in Wuhan, and rapidly spread throughout China. We aimed to clarify the characteristics and clinical significance of peripheral lymphocyte subset alteration in COVID-19. METHODS: The levels of peripheral lymphocyte subsets were measured by flow cytometry in 60 hospitalized COVID-19 patients before and after treatment, and their association with clinical characteristics and treatment efficacy was analyzed. RESULTS: Total lymphocytes, CD4+ T cells, CD8+ T cells, B cells and natural killer (NK) cells decreased in COVID-19 patients, and severe cases had a lower level than mild cases. The subsets showed a significant association with the inflammatory status in COVID-19, especially CD8+ T cells and CD4+/CD8+ ratio. After treatment, 37 patients (67%) reached clinical response, with an increase of CD8+ T cells and B cells. No significant change of any subset was detected in non-response cases. In multivariate analysis, post-treatment decrease of CD8+ T cells and B cells and increase of CD4+/CD8+ ratio were indicated as independent predictors for poor efficacy. CONCLUSIONS: Peripheral lymphocyte subset alteration was associated with the clinical characteristics and treatment efficacy of COVID-19. CD8+ T cells tended to be an independent predictor for COVID-19 severity and treatment efficacy.
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