PGF and asthma: Smoking significantly increased the serum PlGF levels in smokers with asthma [median, interquartile ranges 27.1 (18.6–38.5)] vs. never-smokers with asthma [15.8 (9.6–19.9)] and in healthy smokers [16.3 (10.3–24.8)] vs. healthy never-smokers [10.8 (6.3–14.9)] (Fig. 1A).