Tryptic and elastolytic inhibitory capacities of serum from various Pi phenotypes

Alpha-1-antitrypsin deficiency is responsible for emphysema in adults. The genetic polymorphism of this protein (Pi system) is used to detect these deficiencies. The relationship between the serum protease inhibitory capacities and M, MZ and Z Pi phenotypes was investigated. 120 sera including 31 M, 33 MZ and 56 Z were studied. The alpha-1-antitrypsin concentration varied according to the Pi phenotype, the sex and the health of the subject. The alpha-2-macroglobulin level did not depend on the Pi phenotype. The trypsin inhibitory capacity fluctuated with the age and the health of the subject, but did not faithfully represent the Pi phenotype. In contrast, the elastase inhibitory capacity depended only on the Pi phenotype. The relationship between alpha-1-antitrypsin levels and the serum elastase inhibitory capacities was linear. Canonical analysis was employed to determine the relative contributions of each antiprotease to the two inhibitory capacities. It appeared that the elastase inhibitory capacity was influenced more by the alpha-1-antitrypsin level while the trypsin inhibitory capacity was more sensitive to alpha-2-macroglobulin.