Two‐dimensional electrophoresis of human lymphocyte proteins: Two‐dimensional polymorphisms and paternity testing

Genetic polymorphisms of seven human lymphocyte proteins, analyzed by two‐dimensional electrophoresis, were evaluated in respect to their suitability for paternity testing. Current data of an enlarged family and population study for five proteins (p23, p30, p40, p60, p66), already described for a smaller population sample of Southern Germany, are presented together with evidence for a new polymorphic protein (p42), recently observed in our survey. These six proteins occurred in isoelectric focusing as two different variants, acidic (a) and basic (b). The genetic basis of the protein variations was ascertained (i) by the presence of homozygous and heterozygous phenotypes, (ii) by the Mendelian mode of transmission of the variants as allelic gene products within 17 families and (iii) by the demonstration of a gene‐dosage dependence comparing the spot intensities in homozygous and heterozygous phenotypes. For quantitative data, laser densitometric scanning of the protein spots followed by computer‐assisted quantitative evaluation of the spot intensities was performed. The allele frequencies of the polymorphic proteins were calculated from the phenotype distributions within a sample of 56 unrelated individuals from Southern Germany. Gene frequencies of the common alleles ranged between 0.991 and 0.518. To discuss the suitability of the two‐dimensional polymorphisms for paternity testing the theoretical exclusion probabilities were assessed for seven polymorphic proteins observed in our population sample, the six polymorphisms with two alleles described here and a further polymorphism (p75) with six alleles. For five proteins (p23, p40, p42, p66 and p75) we found sufficiently high values for the theoretical exclusion probabilities, ranging from 10% to 34%. For the seven polymorphic proteins, which could be analyzed on a single two‐dimensional gel, we calculated a combined theoretical exclusion probability of 67%.