We found that PD-1 expression in non-naïve CD8+ T cells correlated with PD-L1 expression and the PD-L1/CD86 ratio in mo 1 (Fig 7I) and to a lower extent also in DC3 (PD-L1: R = 0.34; p = 0.02, PD-L1/CD86: R = 0.37;p = 0.01) indicating potential interaction of this receptor ligand pair in COVID-19. Here, CD86 is linked to COVID-19.