SMYD3 and COVID-19: It is interesting to note that the differentiation of Tregs is subject to regulation by several histone modifications, particularly H3K4me3, which is enriched at the promoter of FOXP3 through the action of a methyltransferase known as SMYD3 [61], although it is not clear whether SMYD3 could be involved in the pathogenesis of COVID-19.