IMMUNOGENETIC POLYMORPHISM OF LIPOPROTEINS IN SWINE: GENETIC, IMMUNOLOGICAL AND PHYSIOCHEMICAL CHARACTERIZATION OF THE TWO ALLOTYPES LPR1 AND LPR2

Abstract

ABSTRACT Results of immunogenetic, immunochemical and physicochemical investigations on two serum allotypes of swine are reported. The allotypes, designated Lpr1 and Lpr2, have been identified by specific alloprecipitins in agar gel. Genetic studies indicate that the allotypes are specified by two codominant autosomal allelic genes, Lpr  1 and Lpr  2. All pigs 3 months of age or older were classified as belonging to one of three phenotypes, Lpr1, Lpr2 or Lpr1,2, each corresponding to one of three genotypes Lpr  1/1, Lpr  2/2 or Lpr  ½, respectively. The Lpr  1 gene was absent or was found at low frequency in the breeds tested. The allotypes were found to occur in two physicochemical forms; in association with chylomicrons and very low density lipoproteins (VLDL) and, primarily, as a Lpr multimer free of the major lipoproteins showing very high density (VHD), d > 1.21 g/ml, and MW ± 190,000. Gel-electrophoretic mobility for VHD-Lpr is different for each of the three Lpr genotypes residing in γ-fast and β-slow regions, but is identical for VLD-Lpr in which Lpr was found complexed with apo-B, migrating as VLDL in the α-2 slow (pre-β) region. Serum levels of Lpr varied during the lifetime and between individuals and, especially, between sera of homozygous pigs being higher in Lpr  1/1 than Lpr  2/2. A linear relationship for Lpr1 and an atypical, inverse relationship for Lpr2 have been observed between the gene dosage, heterozygous vs. homozygous, and the Lpr serum level.