CD4 and COVID-19: Using T cell receptor (TCR)-dependent activation induced marker (AIM) assay, SARS-CoV-2-reactive CD4+ (CD134+CD137+) and CD8+ (CD69+CD137+) T cells (Figure 1B) directed toward S, M, N and other ORFs were detected in 100% and 70% of convalescent patients with COVID-19, respectively (18, 29) (Table 1).