Chen et al. (40) found that the SARS-CoV-2 infection induced a cytokine storm (increase in IL-6, IL-2R, IL-10, and TNFα) and lymphopenia, a decrease in CD4+ and CD8+T cells, as well as suppressed IFN-γ production by CD4+T cells, which might be correlated with disease severity in COVID-19. Here, CD4 is linked to lymphopenia.