Fig. 6From: Safety and long-term improvement of mesenchymal stromal cell infusion in critically COVID-19 patients: a randomized clinical trialAnalysis of cell subpopulation. A Total lymphocytes, B CD3 T lymphocytes, C CD4 T lymphocytes, D Natural killer. Comparison between UC-MSC (red line) and placebo (blue line) groups over time. The bars show standard deviations (SD). *p ≤ 0.05 for comparison between groups (black asterisk). Statistical differences inside groups, longitudinal follow-up, were depicted in the graphs (UC-MSC—red line, placebo—blue line). *p ≤ 0.05 and **p ≤ 0.01 for longitudinal follow-up (red and blue asterisks). Flow cytometry strategy for lymphocyte analysis, total lympohocytes, CD3 T, CD8 T and CD4 T lymphocytes. E Lymphocyte gate FSC/SSC low; F Strong CD45 +  + ; G CD3 positive; H CD4/CD8 dotplot; I CD4 positive. UC-MSCs, umbilical cord mesenchymal stromal cells; SSC, side scatter; FSC, forward scatterBack to article page