CD8A and COVID-19: No consistent differences were observed in T cell numbers among the COVID-19, LRTD and non-LRTD disease groups, but, among patients with COVID-19, there was an expansion in regulatory T cells and proliferating T cells and a decrease in the ratio of effector memory (CD45ROhigh) to naive (CD45ROlow) CD8 T cells (Fig. 2b and Supplementary Table 4).