Pi subtyping by isoelectric focusing: further genetic studies and application to paternity examinations.

Genetic variation of the protease inhibitor (Pi) alpha 1-antitrypsin was analyzed by isoelectric focusing on polyacrylamide gels in a sample of 347 unrelated individuals from Southern Germany. Six common subtypes of PiM were observed as well as the relatively frequent variants PiS and PiZ and the rare variants PiT, Pi less than L, PiL, PiI and PiF. Also, a variant called PiZ1 was found. The frequency of alleles in this sample was PiM1 = 0.6917, PiM2 - 0.1686, PiM3 = 0.0865, PiS = 0.0230, PiZ = 0.0187, and Pi* = 0.0115. In 82 families the distribution of Pi types was in agreement with an autosomal codominant mode of inheritance. The application of Pi classification in cases of disputed paternity is discussed.