For instance, a study revealed that higher proportion of CD25+ FOXP3+ Tregs among CD4+ T cells, increased mean fluorescence intensity (MFI) of FOXP3 and higher expression of activated Treg markers like KLRG1 and PD-1 in severe COVID-19 patients which all reverted to the baseline in the recovered patients (72). This evidence concerns the gene IL2RA and COVID-19.