SERPINA1 and alpha 1-antitrypsin deficiency: Studies aimed at understanding the increased neutrophil burden seen in AATD patients have demonstrated that individuals either homozygous or heterozygous for the Z allele have an increased influx of neutrophils into their lungs.73 A number of models have been proposed to help explain this increase, and one suggestion is the deposition of polymers of mutated Z-AAT protein.