Our data show that sera from COVID-19 patients, especially those with severe disease, contain IgG that intensely recognizes hundreds of intracellular proteins expressed in CD4+ and CD8+ T cells, B cells, NK cells, MAIT cells, γδ T cells, nTregs, and various innate immune cell subsets, including monocytes, neutrophils, eosinophils, and dendritic cells. Here, CD8A is linked to COVID-19.