Joint Report of the Fifth International Workshop on Lymphocyte Alloantigens of the Horse, Baton Rouge, Louisiana, 31 October‐1 November 1987

Abstract

Summary. Six laboratories participated in the Fifth International Workshop on Lymphocyte Alloantigens of the Horse, testing 132 alloantisera against lymphocytes of 880 horses chosen to represent different families and breeds. Most of the alloantisera were produced by lymphocyte immunization between horses matched at the ELA‐A locus. All horses were also tested with antisera contributed to the workshop by participating laboratories which identified ELA specificities A1‐A10 and W12‐W21. Previously identified workshop specificities ELA‐W14, W15 and W19 were accepted as products of the ELA‐A locus based on family and population studies by the workshop. Their designations were changed to ELA‐A14, ELA‐A15 and ELA‐A19, respectively. Two new specificities were identified, namely ELA‐W22 (W22) and ELA‐W23 (W23). Population and family studies indicated that W22 and W23 as well as W13 are products of an ELA locus other than ELA‐A. The presence of these specificities was correlated with the presence of certain ELA‐A locus specificities, e. g. W13 with A3, W22 with A2 and W23 with A5. However, the association was not complete and W13, W22 and W23 also segregated with other ELA‐A specificities in some families. Evidence for recombination was found between the ELA‐A locus and the locus or loci encoding these specificities resulting in seven recombinant haplotypes found among the data presented in this workshop. Further studies are required for definitive assignment of the specificities to a class I or class II locus.

The common equine class I molecule Eqca-1*00101 (ELA-A3.1) is characterized by narrow peptide binding and T cell epitope repertoires

“…ELA) is organized in haplotypes on chromosome 20 comprising up to 15 classical and nonclassical loci as well as pseudogenes (Gustafson et al 2003; Tallmadge et al 2010; Vaiman et al 1986). So far, 19 distinct ELA-A haplotypes have been identified and differentiated serologically (Bailey et al 2000; Lazary et al 1988), with similar levels of polymorphism estimated using intra-MHC microsatellites (Tseng et al 2010) and sequencing (Tallmadge et al 2010). The total number of MHC class I loci expressed on horse cells may vary, but in horses homozygous for the ELA-A3 haplotype at least seven class I molecules can be detected (Azab et al 2014; Tallmadge et al 2005).…”

Equine bone marrow-derived mesenchymal stromal cells are heterogeneous in MHC class II expression and capable of inciting an immune response in vitro

“…All horses were MHC homozygotes of equine leukocyte antigen (ELA) haplotypes ELA-A2, ELA-A3, or ELA-A9, as previously determined by ELA serotyping, direct MHC gene sequencing, and microsatellite typing [27-30]. The Institutional Animal Care and Use Committee of Cornell University approved the use of horses in these studies.…”

Polymorphism at expressed DQ and DR loci in five common equine MHC haplotypes

“…The five MHC haplotypes were originally defined using alloantisera characterized in international workshops (Lazary et al, 1988). MHC homozygosity in these horses was confirmed using multiple independent methods, including selective breeding / segregation, mixed lymphocyte cultures, intra-MHC microsatellite analysis (Brinkmeyer-Langford et al, 2013; Tseng et al, 2010), and direct sequencing of MHC class I (Tallmadge et al, 2010; Tallmadge et al, 2005) and class II genes (this report).…”

“… 1 Determined by ELA serology (Lazary et al, 1988) 2 Breeds: TB – Thoroughbred, SB – Standardbred 3 Use: RT-PCR – Reverse Transcriptase Polymerase Chain Reaction, WGS – Whole Genome Sequence, BAC library – Bacterial Artificial Chromosome large insert library, NGS – Next Generation Sequencing (Illumina paired end libraries). 3 MLC – mixed lymphocyte culture. 5 Polymorphic intra-MHC microsatellite markers using primers characterized in Tseng et al, 2010 and Brinkmeyer-Langford et al, 2013. See Table S1 for details.…”

“…The equine MHC region, designated as the Equine Leukocyte Antigen (ELA) complex, was originally defined using classical serological techniques in international workshops (Lazary et al, 1988). The MHC haplotypes identified using the lymphocyte microcytotoxicity assay were based on polymorphism in MHC class I antigens, which are highly immunogenic in normal equine pregnancy (Antczak et al, 1984).…”