CD4 and COVID-19: Zheng et al. investigated the immune-mediated features of leukocytes in peripheral blood from 16 COVID-19 patients in China, Kunming, and concluded that COVID-19 impaired the CD4 T cells’ functions and caused excessive activation; consequently, lymphopenia caused by CD8+ T-cell depletion may compromise the immune reaction to SARS-CoV-2 in severely ill patients [81].