Monitoring peripheral neutrophil and T-lymphocyte subsets could assist in differentiating the severity and disease progression of coronavirus disease 2019.

Helper T cells (CD3+CD4+ T cells) and cytotoxic T cells (CD3+CD8+ T cells) play direct and indirect antiviral roles. This study retrospectively explored the clinical significance of peripheral lymphocytes, especially the dynamic analysis of T-cell subsets, in determining coronavirus disease 2019 (COVID-19) severity and progression. Seventy-nine patients with COVID-19 in the Public Health Clinical Center of Chengdu from January to February 2020 were included, 59 of which were analyzed for dynamic peripheral T-cell subsets expression. The neutrophil to CD4+ T lymphocyte ratio (N4R) and neutrophil to CD3+ T lymphocyte ratio (N3R) showed clinical significance in differentiating severe or critically-severe COVID-19, with area under receiver operating characteristic curves (AUCs) of 0.933 and 0.900, respectively (P < 0.05). COVID-19 patients with more baseline peripheral lymphocytes or NK cells were prone to test negative to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after therapy (P < 0.05), and the AUC of NK cells for predicting negative results of SARS-CoV-2 RNA detection after therapy was 0.800. When the number of peripheral CD3+CD4+ and CD3+CD8+ T cells in COVID-19 patients continuously increased 6-9 days after baseline, the period of disease exacerbation could be delayed for more than 2 weeks after admission. Baseline N4R and N3R could be potential biomarkers for assisting in differentiating COVID-19 severity, and dynamically monitoring peripheral CD3+CD4+ and CD3+CD8+ T cells 6-9 days after baseline could help clinicians to evaluate disease progression in COVID-19 patients.

Dynamics of NK, CD8 and Tfh cell mediated the production of cytokines and antiviral antibodies in Chinese patients with moderate COVID-19.

Recent studies have demonstrated a marked decrease in peripheral lymphocyte levels in patients with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Few studies have focused on the changes of NK, T- and B-cell subsets, inflammatory cytokines and virus-specific antibodies in patients with moderate COVID-19. A total of 11 RT-PCR-confirmed convalescent patients with COVID-19 and 11 patients with non-SARS-CoV-2 pneumonia (control patients) were enrolled in this study. NK, CD8+ T, CD4+ T, Tfh-like and B-cell subsets were analysed using flow cytometry. Cytokines and SARS-CoV-2-specific antibodies were analysed using an electrochemiluminescence immunoassay. NK cell counts were significantly higher in patients with COVID-19 than in control patients (P = 0.017). Effector memory CD8+ T-cell counts significantly increased in patients with COVID-19 during a convalescent period of 1 week (P = 0.041). TIM-3+ Tfh-like cell and CD226+ Tfh-like cell counts significantly increased (P = 0.027) and decreased (P = 0.022), respectively, during the same period. Moreover, ICOS+ Tfh-like cell counts tended to decrease (P = 0.074). No abnormal increase in cytokine levels was observed. The high expression of NK cells is important in innate immune response against SARS-CoV-2. The increase in effector memory CD8+ T-cell counts, the up-regulation of inhibitory molecules and the down-regulation of active molecules on CD4+ T cells and Tfh-like cells in patients with COVID-19 would benefit the maintenance of balanced cellular and humoural immune responses, may prevent the development of severe cases and contribute to the recovery of patients with COVID-19.