CD4 and COVID-19: Its real function in the control of the infection is uncertain: on one hand, miR-155 could play a protective role via CD4+ T cell regulation and by affecting CD8+ T cell responses [42,43]; on the other hand, lung injury by acute respiratory distress syndrome (ARDS) was attenuated by the deletion of miR-155, making this miRNA a potentially harmful player in the context of COVID-19.