CD8A and COVID-19: A peripheral lymphopenia with decreased counts of total T cells, CD4+ and CD8+ T cells and natural killer (NK) cells is characteristic of COVID-19; the CD8+ cells are decreased more significantly than CD4+, and both of them show the surface expressions of several T cell exhaustion markers and other functional impairments like decreased proliferation and production of IFN-γ and TNF-α [5-9].