CD8A and COVID-19: scSeq of transcriptomes and immune repertoires in COVID-19 patients with severe symptoms has shown a high level of clonal expansion in specific T cell subsets (Th1, Th2, and Th17) and preferential germline gene usage in clonally expanded B cells (28, 34, 37); while a more recent study found a positive correlation between clonal expansion of effector-like CD8+ T cells and disease severity (38).