IFNG and chronic obstructive pulmonary disease: We compared cytokine levels among COPD patients; the serum of COPD-TS has higher levels of IL-4 in comparison with COPD-BBS (102.9 pg/μL vs. 28.7 pg/μL) and the same to IFN-γ (13.9 pg/μL vs. 36.7 pg/μL, respectively); however, COPD-BBS has higher levels of IL-6 and IL-10 concerning COPD-TS (Table 4).