CD8A and COVID-19: Strikingly, TRBV6-4, which showed the most significant difference in the CD8+ compartment, being underrepresented in the active COVID-19 cohort, is disproportionately expressed by “unconventional” CD8+ mucosal-associated invariant T cells that have been described as severely cytopenic in COVID-19 (35) (Fig. 3A).