For instance, one recent research found that severe COVID-19 patients had greater levels of CD25+ FOXP3+ Tregs among CD4+ T cells, increased FOXP3 expression, and elevated production of activated Treg markers including KLRG1 and PD-1, all of which returned to normal levels in the recovering individuals or convalescent patients [51]. This evidence concerns the gene FOXP3 and COVID-19.