After correcting the data for the sex of the participants, we observed that many inflammatory markers and changes in cell populations linked with severe COVID-19 correlate with age in healthy individuals," explains senior co-author Professor Mihai Netea, also of Radboud University Medical Center, Nijmegen, Netherlands.
These parameters include changes to white blood cells including increased non-classical monocyte numbers, a critical decrease in T lymphocytes, particularly some types of CD8+ and CD4+ lymphocytes and naïve regulatory T cells, elevated circulating levels of monocyte chemoattractant protein 1 (MCP1) that induces immune cell accumulation in organs, osteoprotegerin (OPG) that may increase survival of certain cell populations, hepatocyte growth factor (HGF) that activates both immune and epithelial cells, and declined concentrations of receptor activator of nuclear factor kappa-Β ligand (RANKL/TRANCE). Interleukin-6, a marker of inflammation and one of the major biomarkers of COVID-19 severity, also increases with age in both cohorts.
The authors conclude: "Age is one of the biggest risk factors of COVID-19 severity and fatality. Our results suggest that the severe COVID-19 immunological profile, represented by changes in cell populations and circulating inflammatory proteins, is already partly present in aged healthy individuals. Therefore, some of these dysregulations might not be a direct result of the infection but rather an underlying profile that is permissive to a more severe form of the disease.
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If blood tests could identify these individuals early, they could decide whether to strictly isolate themselves.
