Porcine IL12A and IL12B gene mapping, variation and evidence of association with lytic complement and blood leucocyte proliferation traits.

Interleukin-12, a heterodimeric cytokine consisting of glycosylated subunits of 35 and 40 kDa, is a central molecule in controlling innate as well as adaptive immunity. This study was aimed to investigate the role of IL12A and IL12B as candidate genes for immune competence in pigs. The porcine genes were screened for polymorphism and association analysis was carried out by mixed model analysis with parameters of innate immunity, in vitro haemolytic complement activity in the classical and alternative pathways, in vivo complement activation expressed as C3c serum concentration, and blood leucocyte proliferation measured in F2 animals of a pig resource population based on cross of Duroc and Berlin miniature pig (DUMI resource population). A single nucleotide polymorphism (SNP) in the promoter region (C > A) of IL12A was identified. Two SNPs were detected in intron 4 of IL12B at positions 192 (A > G) and 437 (C > T). Significant effects of IL12 genotypes on complement activity traits and mitogen-induced leucocyte proliferation were found. The IL12A and IL12B genes were assigned to chromosome13 and 16, respectively, by using radiation hybrid analysis and genetic mapping in the DUMI resource population. Mapping and association analyses promote the IL12 genes as functional and positional candidate gene for disease resistance in pigs.