CD69 and COVID-19: Large studies from Oxford(64) and Paris(61) again observed a significant, 90% reduction of circulating MAIT cells in COVID-19, upregulation of granzyme B and CD69 on NK, CD8+ T, γδ T and particularly MAIT cells, and confirmed the correlation between the outcome of SARS-CoV-2 infection and MAIT cell activation and cytotoxicity (Figure 1B)(61).