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Running title: Monocytes and antigen-specific T-cells in severe COVID-19. 

Authors:Payen D et al. 

Journal/ Pre-Print:medRxiv 

Tags: Clincal, Immunology/Immunity 

Research Highlights

  1. No significant differences in monocyte subset populations over time in severe COVID19 hospitalised patients 

  1. Although a reduction of CD4 and CD8 T cells was observed, the CD4/CD8 T cells ratio remain the same throughout 

  1. SARS-CoV2 specific CD4 T cells were more potent in secreting cytokines (IFNgTNFa, IL-2) than CD8 T cells after in vitro stimulation. 


A longitudinal study following 15 severe COVID-19 patients, not on immunomodulatory treatment, to assess lymphocyte subsets and their functionality and monocyte phenotyping in serial peripheral blood samples.  As previously reported, a decrease in CD4 and CD8 T cells was observed in severe patients, however no disruption of the CD4/CD8 ratio is shown. Isolation of SARS-COv2-specific T cells showed that after in vitro stimulation CD4 T cells were more capable of secreting cytokines (IFNgTNFa, IL-2) with higher TNFa, IL-2 positive cells. Overall this study lacks a strong correlation/explanation between their observations.  

Impact for SARS-CoV2/COVID19 research efforts 

Understand the immune response to SARS-CoV2/COVID19  

Study Type  

  • Clinical Cohort study (15 patients followed overtime with blood collections) 

Strengths and limitations of the paper 

Novelty: The authors assess the functional potential of the cells by looking at expression of multiple cytokines and monocyte populations overtime.  

Standing in the field: This study does not add crucial data to the field.   

Appropriate statistics: Yes, but small sample size 

Viral model used: Severe COVID-19 hospitalized patients (confirmed by RT-PCR) 

Translatability: It would be very interesting to deeper phenotype innate and adaptive immune responses overtime in different disease stages in patients. However, the translational implications of the research are limited. 

Main limitations:  

  • Study lacks details of monocyte subsets and their potential roles. Moreover, the study was confined to analyses of peripheral blood and did not look at macrophages. 

  • Did not show the gating strategy neither the MFI for cytokine production for instance 

  • Limited sample size (n=5 patients for cytokine experiments) 

  • Did not entirely functionally characterise the cells. It would have been valuable if they had phenotyped SARS-Cov2 specific T cells by FACS over time.