GZMB and infection: No change in cytokine release (4 h after reactivation) was observed when the CD8+ T cells were incubated in 21% or 5% oxygen, but when reactivation was performed at 1% oxygen, levels akin to the tumor microenvironment or sites of infection, ML226-treated CD8+ T cells showed reduced secretion of interferon γ (IFNy), granzyme B and Fas ligand (FASL; Fig. 6e).