TNF and chronic obstructive pulmonary disease: Inflammatory cytokines induced by pneumonia‐related bacteria, such as Haemophilus influenzae and Streptococcus pneumoniae, are important in COPD exacerbation [4, 42, 43], and TNF‐α and IL‐6 levels are increased in sputum during COPD exacerbations [7, 44].