CD4 and COVID-19: Although CD4 T helper cells are essential for B-cell maturation, germinal center (GC) formation and Ig affinity maturation [19, 20, 28], we recently reported that CD4 T cells from COVID-19 individuals were more prone to die by apoptosis, which is prevented by using a caspase inhibitor, not by using pyroptosis or necroptosis inhibitors [27].