The severity of covid-19 is due to very severe pneumonia and multiple organ failure. This is believed to be the result of an induced cytokine storm as a result of a SARS-CoV-2 virus infection. To suppress cytokine storms, Inhibitors of cytokines such as IL-6, IL-1, and GM-CSF are being considered, but further improvements are needed to reduce mortality.
The following group has proposed the importance of IL-10 in addition to the current strategies.
https://www.cell.com/action/showPdf?pii=S1471-4906%2820%2930256-8
IL-10 is generally recognized as an anti-inflammatory cytokine. However, IL-10 function seems to be multifaceted, and there have been some reports of IL-10 often acting as an inflammatory cytokine in the treatment of melanoma, renal cell carcinoma, and non-small cell lung cancer. In COVID-19, IL-6 and IL-10 are very highly expressed among various cytokines as infected with viruses and become more severe. So clinically speaking, IL-6 and IL-10 are identified as covariates that accurately predicted disease severity.
In the early stage of infection, IL-10 might be acting as an anti-inflammatory cytokine as a balancer as inflammation progresses, but it might be acting as an inflammatory cytokine when it becomes more severe. Therefore, the timing of IL-10 blocking is critical, but it may be effective to use IL-10 inhibitors together with IL-6 inhibitors.
Experimental validation will be a task of the future.