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Authors: Yang, et al., 2020 

Journal/ Pre-PrintMedRxiv 

Tags: Immunology/Immunity 

Research Highlights 

  1. Selective lymphopenia of CD4+ T cells in COVID-19 recovered individuals compared to healthy donors. 

  1. Alterations in subset make up of both CD8+ and CD4+ T cells of COVID-19 recovered individuals compared to healthy donors.  

Summary 

This study examines phenotypic alterations in lymphocytes of 55 COVID-19 recovered patients compared to 55 age matched healthy donors. With respect to overall frequency, CD8+ T cells and B cells were comparable, yet there was a significant decrease in CD4+ T cells in the recovered cohort. Interestingly, there were subset variations amongst CD8+ and CD4+ cells. This study is limited in that patients only donated one sample and therefore changes over time were not observed. Furthermore, there was a lack of analysis of functional variation of the different populations across the cohorts.  

Impact for SARS-CoV2/COVID19 research efforts  

Understand the immune response to  SARS-CoV2/COVID19  

  • Further strengthens the argument that there is an aberrant T cell response to SARS-CoV-2 infection relative to healthy donors.  

  • This is particularly highlighted in the reduced number of Tcm cells in recovered patients compared to healthy donors.   

Study Type  

  • Clinical Cohort study 

Strengths and limitations of the paper 

Novelty:  

Standing in the field:Adds weight to the growing opinion that there is an aberrant lymphocyte response, particularly that of T cells, in response to SARS-CoV-2 infection.   

Appropriate statistics: T-test used throughout despite no evidence that data sets are normally distributed. Some plots, particularly those in Fig 2, clearly show a skewed data set and therefore a non-parametric test would be more appropriate.  

Viral model used:Patients who had recovered from SARS-CoV-2 infection. 

Translatability:n/a 

Main limitations:  

  • Co-morbidities of recovered patients not shown, therefore donors may not be matched in this regard.  

  • This study solely examined surface markers, or the expression of cytokines in a binary way. Single-cell gene expression studies of lymphocytes are likely to be more fruitful in examining how the phenotypic changes seen in lymphocytes of COVID-19 patients pertains to aberrant function. 

  • Poor statistics  

  • Very heterogeneous responses within groups indicating that larger group sizes are needed to detect true significance. Also unclear what the biological significance is of some of the differences  

  • Only percentages of populations shown, would have been useful to see absolute cell counts