Discussion
In the present study, among 105 patients with severe COVID-19, 44.8% patients (47/105) showed decreased CD4+T cells count and the in-hospital death was markedly higher in patients with decreased CD4+T cells count than in patients with normal CD4+T cells count (42.6% vs 3.4%,P <0.001). In addition, our study found that increased age, increased white blood cell count, and decreased platelet count were associated with in-hospital death, which were similar with several studies. Verity, et al. estimated that the total case fatality rate increased with age, possibly because they often had other chronic diseases4. Wang, et al. suggested that white blood cell count and neutrophil count of dead patients were higher than those of surviving patients, which may be related to cytokine storm caused by the invasion of SARS-Cov-25. Meanwhile, A meta-analysis showed that there was a significant reduction in platelets in patients dying from COVID-19, and low platelet count was associated with mortality in patients with COVID-19; The reason may be the decrease of the number of pulmonary vascular beds and the change of morphology that lead to deranged platelet defragmentation6.
Several recent studies indicated that T-lymphocytes1,7was reduced in most patients with COVID-19. It was believed that SARS-CoV-2 may act mainly on lymphocytes, especially T-lymphocytes2,8. At present, the potential mechanisms undergoing CD4+T cells count decrease induced by SARS-CoV-2 infection is still unknown. Researchers suggested the decrease in the number of T-cells in patients with COVID-19 may be due to the negative effects of high concentrations of TNF-α, IL-6, IL-10 in serum on the survival or proliferation of T-cells7. In addition, Previous studies have shown that, in SARS patients, the formation of autoimmune antibodies or immune complexes induced by viral infection and the use of steroids may play an important role in lymphocytic decline9.
In conclusion, the main finding of this study is the high prognostic value of decreased CD4+T cells count in patients with severe COVID-19. Thus, in this acute-care setting, CD+4 T cells count can provide early prognostic information in patients with severe COVID-19.