KLF4 and alpha 1-antitrypsin deficiency: To our knowledge, so far only one study has shown an enhanced expression (2.1-fold) of Krüppel-related zinc finger protein (specifically undefined) in lung tissue from patients with AATD-associated emphysema when compared to normal lung tissue [26] and it has been shown that KLF4 mRNA is up-regulated more than 10-fold in mice lung tissue after endotoxin stimuli [27].