CD8A and COVID-19: Additionally, CD8+ T cell- and NK cell-attracting cytokines are upregulated in SARS-CoV-2-infected human lung cells and in lung tissues from COVID-19 patients, and the levels of CD8+ T cells and NK cells are higher in bronchoalveolar lavage fluids from mildly affected COVID-19 patients than in patients with severe disease (46, 47).