15.  Total: 68 Mild/Moderate: 55 Severe: 13  • Decreased number of CD8+ T and NK cells in patients showing severe symptoms.• Decrease in expression of IFN-γ, IL-2, granzyme-B by CD8+ T, and decrease in TNF-α expression by NK cells was observed, indicating CD8+ T and NK cell exhaustion.  Peripheral blood/Serum  (Zheng M. et al., 2020)