MKI67 and COVID-19: In contrast, SARS-CoV-2-specific HLA-I multimer+ CD8+ T cells from severe COVID-19 patients express activation markers (CD38 and HLA-DR), inhibitory receptors (PD-1, TIM-3, and LAG-3), cytotoxic proteins (GrZB and perforin), and Ki-67, representing that these cells are activated and proliferate with a high cytotoxic capacity.