TNF and chronic obstructive pulmonary disease: The levels of PlGF in BAL fluid were also significantly higher in patients with COPD than in controls (45.7 (12.3) pg/ml vs 23.9 (7.6) pg/ml, p = 0.005), associated with an increase in the cytokines tumour necrosis factor-α (TNF-α) and interleukin-8 (IL-8).