CD8A and COVID-19: Besides, the frequency of terminally differentiated effector memory CD8+ TEMRA within CD8+ T cells was significantly increased in the presymptomatic, mild and moderate COVID-19 cases as compared to the asymptomatic groups (Fig. 2l and Supplementary information, Fig. S3b).19 Taken together, these results indicated a plausible T cell exhaustion in the presymptomatic group rather than in the asymptomatic group.