Characterization of the swine major histocompatibility complex alleles at eight loci in Westran pigs

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Abstract
Background: Pigs are an important large animal model for transplantation and a potential source of xenografts. Swine leukocyte antigen (SLA) molecules are strong mediators of alloreactive and xenoreactive immune responses. We have characterized the SLA alleles of a new pig line bred for transplantation research, the Westran (Westmead Hospital transplantation) pig, described in a companion paper. Methods: Three sixth generation inbred Westran pigs and a Large White pig control were used to assess SLA alleles. We examined the SLA‐1, SLA‐3, SLA‐6, SLA‐2, DQA1, DQB1, DRA1 and DRB1 loci using reverse transcription‐polymerase chain reaction and sequencing‐based method. Results: All of the Westran pigs had a single allele at each locus, except for the SLA‐1 locus. Typing of the SLA‐1 locus in additional animals indicated that this is most likely the result of a duplication of the SLA‐1 locus rather than heterozygosity. The lack of SLA heterozygosity is consistent with the previous finding of low microsatellite marker heterozygosity and is the result of both the recent deliberate inbreeding of these pigs and their derivation from a feral stock from Kangaroo Island, South Australia, established by the release of a single pair in 1803. Conclusions: After comparing DNA and protein sequences of the Westran SLA alleles with published GenBank SLA sequences, the SLA class I alleles found in the Westran pigs were all novel, while the SLA‐DR and DQB1 alleles have been previously described in other pig breeds. Characterization of the SLA alleles in the Westran pigs has identified novel alleles and will be useful for designing protocols for modulation of immune responses to allografts and xenografts.