GZMB and COVID-19: We then investigated CD4+, Treg and CD8+ T cells polyfunctionality by analyzing simultaneous production of TNF-α, CD107a, IFN-γ, IL-2, IL-17, granzyme-B and TGF-β by mild, moderate and severe COVID-19 convalescent patients at recovery time-point I and time-point II, as well as by healthy donors (Figure 6).