Isoelectric focusing in immobilized pH gradients for the determination of the genetic Pi (α₁‐antitrypsin) variants

The genetic variants of the human protease inhibitor (Pi) system have been analyzed by isoelectricfocusing in immobilized pH gradients. With the use of a narrow pH range of pH 4.50 to 4.70 the six common PiM subtypes can be readily and reliably classified. The less common inherited Pi variants can be demonstrated most clearly in a gradient of pH 4.4 to 4.8. For the classification of PiZ a more basic pH gradient of 4.55 to 5.05 has been employed. Isoelectric focusing with immobilized pH gradients is also a useful tool for the study of the genetic variation in the Pi system. A number of problems to be adressed in future studies are discussed such as the delineation of further PiM subtypes, the detection of additional inherited heterogeneity, and the application of isoelectric focusing with immoblilized pH gradients in routine typing laboratories.