IFNG and chronic obstructive pulmonary disease: CD8 T cells, which are another major source of IFN-γ, have been reported to increase in number and be more prone to secreting cytokines due to CS in patients with chronic obstructive pulmonary disease (COPD) [103,104,105,106,107], and low soluble programmed death protein 1 ligand (sPD-L1) levels [108] and increased activated cytotoxic CD8 T cells [109] were also reported in RA patients.