Distribution of the CD4 Alleles in Sus scrofa Demonstrates the Genetic Profiles of Western Breeds and Miniature Pigs.

Widely used antipig CD4 monoclonal antibodies (mAbs) fail to recognize CD4 alleles characteristic of miniature pig lines such as the National Institutes of Health (NIH) miniature pigs and microminipigs. We surveyed polymorphisms in the coding sequence of the porcine CD4 gene among Western and Oriental pig breeds and Japanese wild boars and investigated their distribution. Of the 13 alleles that we identified among the 47 animals, 2 in group I and 3 in group II were found exclusively in Western breed pigs. Group IV alleles, which included mAb-nonbinding alleles, were found frequently in Oriental breed pigs, suggesting that the mAb-nonbinding allele arose from the gene pool of Oriental pigs. Group IV alleles were also found in Duroc and Large White pigs, suggesting genetic inflow from Oriental pig breeds into Western breeds. Comparison of the CD4 sequences of species in Cetartiodactyla suggested that the group IV alleles in Sus scrofa occurred before the divergence of this species from the other artiodactyls. The different antibody specificities of the various CD4 alleles may facilitate the discrimination of T-cell populations in transplantation studies using miniature pigs. The significance of the preservation of CD4 polymorphisms to immune function in pigs warrants further investigation.