Regulatory CD4+ and CD8+ T cells are negatively correlated with CD4+/CD8+ T cell ratios in patients acutely infected with SARS-CoV-2

Abstract

Regulatory T cell can protect against severe forms of coronaviral infections attributable to host inflammatory responses. But its role in the pathogenesis of COVID-19 is still unclear. In this study, frequencies of total and multiple subsets of lymphocytes in peripheral blood of COVID-19 patients and discharged individuals were analyzed using a multicolor flow cytometry assay. Plasma concentration of IL-10 was measured using a microsphere-based immunoassay kit. Comparing to healthy controls, the frequencies of total lymphocytes and T cells decreased significantly in both acutely infected COVID-19 patients and discharged individuals. The frequencies of total lymphocytes correlated negatively with the frequencies of CD3^- CD56⁺ NK cells. The frequencies of regulatory CD8⁺ CD25⁺ T cells correlated with CD4⁺ /CD8⁺ T cell ratios positively, while the frequencies of regulatory CD4⁺ CD25⁺ CD127^- T cells correlated negatively with CD4⁺ /CD8⁺ T cell ratios. Ratios of CD4⁺ /CD8⁺ T cells increased significantly in patients beyond age of 45 years. And accordingly, the frequencies of regulatory CD8⁺ CD25⁺ T cells were also found significantly increased in these patients. Collectively, the results suggest that regulatory CD4⁺ and CD8⁺ T cells may play distinct roles in the pathogenesis of COVID-19. Moreover, the data indicate that NK cells might contribute to the COVID-19 associated lymphopenia.