The Recent Update of the Swine Leukocyte Antigen (SLA) Nomenclature System

The swine leukocyte antigen (SLA) system is among the most well characterized MHC systems in non-human animal species. The International Society for Animal Genetics (ISAG) and International Union of Immunological Societies Veterinary Immunology Committee (IUIS VIC), SLA Nomenclature Committee was formed in 2002. The committee's primary objectives are: 1) to validate newly identified SLA sequences according to the guidelines established for maintaining high quality standards of the accepted sequences; 2) to assign appropriate nomenclatures for new alleles as they are validated; and 3) to serve as a curator of the IPD-MHC SLA sequence database (http://www.ebi.ac.uk/ipd/mhc/sla/), which is the repository for all recognized SLA genes, their allelic sequences and haplotypes. To date, there are 155 classical class I (SLA-1, SLA-2, SLA-3), 13 non-classical class I (SLA-6, SLA-7 and SLA-8) and 182 class II (DRA, DRB1, DQA, DQB1, DMA) alleles officially designated. There are 39 class I and 31 class II haplotypes at the high-resolution (allele) level designation. Recent evidence has suggested certain loci in the SLA system previously recognized as pseudogenes (e.g. SLA-9, SLA-11, DQB2 and DOB2) may be expressed at the transcript level for some haplotypes; the committee will determine if designation of the alleles of these loci is warranted as more evidence accumulates. A systematic nomenclature for the genes, alleles and haplotypes of the swine MHC is critical to the research in swine genetic diversity, immunology, health, vaccinology, and organ or cell transplantation. Continuous efforts on characterizing SLA alleles and haplotypes and studying of their diversity in various pig populations will further our understanding of the architecture and polymorphism of the SLA system and their role in disease, vaccine and allo- or xeno-graft responses.