A "new" genetic polymorphism of a human serum protein: inter-alpha-trypsin-inhibitor.

A new genetic polymorphism of a human serum glycoprotein, the inter-alpha-trypsin-inhibitor (ITI), has been demonstrated by population and family studies. Sera were examined after neuraminidase treatment by isoelectric focusing on agarose gels followed by immunoblotting or by immunofixation with specific ITI-antiserum. Using this method, three common ITI phenotypes 1, 1-2 and 2, as well as two further rare ITI types 1-3 and 2-3 were disclosed. Genetically, these phenotypes are controlled by three allelic genes that determine a total of six phenotypes. These alleles are designated ITI*1, ITI*2 and ITI*3. The homozygous form of the third allele ITI*3 has not been found, as yet. The frequencies of ITI were examined in two population samples from Southern Germany (n = 248) and from Tyrol, Austria (n = 124). The gene frequencies of the common alleles ITI*1 and ITI*2 were 0.575 and 0.417, respectively, in Southern Germany, and 0.577 and 0.423, respectively, in Tyrol, Austria. The third allele ITI*3 was found only in the sample from Southern Germany, thus far, and was calculated to be 0.008.