CD4 and COVID-19: In this study, recovery from severe COVID-19 led to increases in proinflammatory cytokine responses from CD4+ and CD8+ T cells including TNFa, IL-2, IFN-g and CD107a at 3 months, followed by a significant decrease in these responses at the long-term timepoint (6 months), indicating a shift to an immunologically exhausted state of the CD4+ and CD8+ T cells [146].