Except for tissue protection during pneumonia via the activation of STAT3 (signal transducer and activator of transcription 3) [105], and an unequivocal role in apoptosis (some authors suggest it has proapoptotic properties [106,107], while others find it anti-apoptotic [108,109]), LIF had been previously shown to play a role in airway hyperresponsiveness; its neutralization enhances AHR and airway reactivity to methacholine [102,110]. This evidence concerns the gene STAT3 and airway hyperresponsiveness.