PGF and chronic obstructive pulmonary disease: The increased levels of PlGF in patients with COPD may result from the stimulation of proinflammatory mediators, as we found an increase in proinflammatory cytokines in BAL fluid of patients with COPD and a bronchial epithelial cell line (S-cells) was shown to express PlGF after exposure to a variety of proinflammatory cytokines.