CD8A and COVID-19: In particular, the expression of PD-1 and ICOS on CD4+ T cells and that of CD127 and CD40L on CD8+ T cells showed a marked decrease when the majority of blocking antibodies were added, both individually and as a pool, to PBMCs cultured with serum obtained from patients with COVID-19 (Figure 2C and Supplemental Figure 3, A and B).