CD4 and infection: Therefore, the results of Ld-IL2 therapy in COVID-19 patients will be informative and helpful to understand the multiple roles of Ld-IL2 therapy in controlling infection, expanding TREG cells [79], regulating CD4+ T cell subsets [82,85], enhancing CD8+ T cells activation or exhaustion [83] or potentially inducing bystander CD8+ T cell-mediated immunopathology [86] in COVID-19 and other disease.