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Authors: Hasichaolu et al.,  

Journal/ Pre-Print:MedRxiv 

Tags: Immunology/Immunity, Inflammation, Clinical 

Research Highlights  

  1. Compared to healthy controls, two-week post-recovery patients had lower absolute numbers of total lymphocytes including CD4+ T cells, CD8+ T cells, and CD56+ NK cells. 

  1. Higher levels of cytokines including IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ and IL-17 detected in recovered patients compared to healthy controls. 


Accumulating data demonstrate immune cell dysregulation in COVID-19 patients. This study characterized immune subsets and cytokines levels in 33 two-week post-recovery COVID-19 patients and 28 healthy volunteers. Consistent with previous findings, low cell counts of circulating T cells and NK cells was observed in the recovered patients compared with healthy controls. The concentrations of serum cytokines including IL-2, IL -4, IL -6, and IL-17 were higher than controls, suggesting ongoing inflammation 2-weeks post-recovery. However, the decline in the blood lymphocyte subsets and the increased level of cytokines were reported to be an independent predictor of rehabilitation efficacy. The study suggests that medical observation may be needed following COVID-19 recovery. However, longitudinal analysis of a larger cohort is required to fully investigate immune status during symptomatic and recovery stages. 

Impact for SARS-CoV2/COVID19 research efforts  

Understand the immune response to SARS-CoV2/COVID19  

Clinical symptoms and pathogenesis of SARS-Cov2/COVID19 

Study Type  

  • Clinical Cohort study

Strengths and limitations of the paper 

Novelty: The study supports the medical mentoring of hospitalized patients after hospital discharge. 

Standing in the field: The decline in lymphocytes has been reported in other studies ((Divij Mathew et al. science 2020). This study therefore supports previous findings.   

Appropriate statistics: Yes 

Viral model used:SARS-CoV-2  

Translatability: limited translatability.    

Main limitations:  

  1. Some variability of CD4 T cell counts and some cytokine levels were observed in the data. This variability could be explained by differences in disease severity. 

  1. NK cells were defined on the basis of the CD56 marker. While other studies may have used the same method, this gating strategy could potentially exclude NK subsets expressing low CD56 which has been reported to be expanded in SARS-CoV2 patients (Rita Carsetti et al, 2020). 

  1. The sample size of the cohort is relatively small which could impact on statistical power. 

  1. Previous findings reported higher CD4:CD8 ratio in acute COVID-19 patients (Divij Mathew et al. science 2020) which was not detected in this study. This could be explained by the differences in the infection stage, but further explanation/discussion will be helpful. 

  1. Only one time point was studied therefore it is unclear whether the immunological parameters observed in the recovered patients were returning to normality or whether there was evidence of long-term dysregulation.