The A system of horse erythrocyte alloantigens: a new allele and another look at factor Ae

Family data are presented for a new allele (Aabdg) in the A system of horse erythrocyte alloantigens which includes factors Aa and Ab traditionally thought to be products of allelic genes. Evidence for incorrect assignment of the codominant factor Ae in the presence of Ab and Ac and the absence of Aa is discussed.     

Expansion of the D system of horse red cell alloantigens

Two additional specificities (Dq and Dr) were assigned to the D system of horse red cell alloantigens following discussion of the 1989 ISAG Horse Comparison Test (HCT) results. Family and population data support 25 phenogroups defined by the enhanced battery of 17 D system factors.     

A new phenogroup in the horse D system of red cell alloantigens found in the Caspian pony

A new D blood group phenogroup consisting of the specificities adeo was observed in a stallion family of Caspian ponies from Iran. An additional six undescribed genetic variants were seen in a total of 82 Iranian horses. This result suggests extensive new genetic variation may be present in domestic horses from geographic regions that have not yet received scientific attention.     

Unusual D system inheritance in Anglo-Arab horse

An unusual D system phenogroup appeared in one family line of Anglo-Arab horse. This phenogroup probably originated from inheritance with an apparent absence of factors and was transmitted through successive generations.     

Linkage disequilibrium between the ELA and the A blood group systems in Standardbred horses

The linkage group formed by the ELA and A blood group system in horses was studied in American Standardbred horses. The distance between the ELA locus and the A blood group locus was measured as 1.61 centimorgans. observing only the haplotypes contributed by the sires.
Strong linkage disequilibrium was found in pacing Standardbred horses for ELA-W1 with Aa, ELA-W5 with Ab and ELA-W10 with Ab. Linkage disequilibrium was apparent at both the population and family level. Among trotting Standardbred horses, linkage disequilibrium was found for ELA-W1 with Aa and for ELA-W10 with Ab. It was not possible to investigate linkage relationships in Thoroughbred horses because of the high frequency of Aa and low frequency of other A system markers.     

Blood group and protein polymorphism gene frequencies for seven breeds of horses in the United States

Gene frequencies at 20 blood group and protein polymorphism loci ( A, C, D, K, P, Q, U, Al, Tf, Pi, Xk, Es, Gc, PGD, CA, Cat, PGM, AP, Hb and PHI ) are given for seven horse breeds in the United States (Thoroughbred, Arabian, Standard bred, Morgan, Quarter Horse, Paso Fino and Peruvian Paso). These data are used to calculate that the battery of tests is at least 96% effective for recognizing incorrect paternity in these breeds. In addition to paternity testing, these tests can be applied to studies of breed relationships.     

Protease inhibitor system in horses: classification and detection of a new allele

A method of horizontal thin layer polyacrylamide gel electrophoresis at acid pH has been developed for the separation of the prealbumins in equine plasma. Using this method, it has been possible to split the S allele into two, S₁ and S₂, bringing the total number of prealbumin alleles in Thoroughbred horses to eight. The gene frequencies of these eight alleles in Australian Thoroughbreds are presented. All eight prealbumin types exhibit antiprotease activity and therefore, it is suggested that the name prealbumin (Pr) should be abandoned in favour of protease inhibitor (Pi) although at this stage it is not known whether this incorporates the Pi1 and Pi2 described by Juneja et al. (1979).     

Population genetics of Great Basin feral horses

The genetic make-up of Great Basin wild (feral) horses was investigated by blood typing studies. Blood samples of 975 feral horses from seven trap sites in Nevada and Oregon were tested by serological and electrophoretic techniques for genetic markers at 19 polymorphic loci. The average number of variants for the seven feral populations [72·1 ± 3·2 (SEM), range 62–85] was not significantly different from that of 16 domestic breeds (75·0 ± 11·5, range 58–105). The expected average frequency of heterozygotes per locus (average heterozygosity) for the feral populations (0·402 ± 0·009, range 0·368–0·442) was not significantly different from the domestic breeds (0·389 ± 0·045, range 0·295–0·443). Dendrograms constructed using pairwise comparisons of Nei's distance measurements substantiated anecdotal accounts of the origins of Great Basin horses from Iberian, American saddle horse and draft horse breeds.     

A pedigree-based study of mitochondrial D-loop DNA sequence variation among Arabian horses

Through DNA sequence comparisons of a mitochondrial D-loop hypervariable region, we investigated matrilineal diversity for Arabian horses in the United States. Sixty-two horses were tested. From published pedigrees they traced in the maternal line to 34 mares acquired primarily in the mid to late 19th century from nomadic Bedouin tribes. Compared with the reference sequence (GenBank X79547), these samples showed 27 haplotypes with altogether 31 base substitution sites within 397 bp of sequence. Based on examination of pedigrees from a random sampling of 200 horses in current studbooks of the Arabian Horse Registry of America, we estimated that this study defined the expected mtDNA haplotypes for at least 89% of Arabian horses registered in the US. The reliability of the studbook recorded maternal lineages of Arabian pedigrees was demonstrated by haplotype concordance among multiple samplings in 14 lines. Single base differences observed within two maternal lines were interpreted as representing alternative fixations of past heteroplasmy. The study also demonstrated the utility of mtDNA sequence studies to resolve historical maternity questions without access to biological material from the horses whose relationship was in question, provided that representatives of the relevant female lines were available for comparison. The data call into question the traditional assumption that Arabian horses of the same strain necessarily share a common maternal ancestry.     

Genetic linkage between loci for a red cell alloantigen (U) and serum protease inhibitor (Pi) in the horse

Preliminary evidence for the fifth autosomal linkage group in the horse, comprised of the loci for a red cell alloantigen (U) and serum protease inhibitor (Pi), was demonstrated by means of paternal half-sib groups in thoroughbred, standardbred and Arabian breeds. Recombination frequency in males was estimated to be 0.125 +/- 0.019.     

A contribution to the D system in horses*

The inheritance of a new D system red cell antigen, factor 22, is described. It has also been possible to discriminate more efficiently between D system pheno-groups enabling genotypes to be identified from phenotypes in the majority of cases. This improves the accuracy of animal identification and gene frequency estimates.     

Population data and a fourth allele for equine complement component 3 (C3)

The C3 polymorphism of equine serum or plasma revealed by agarose gel electrophoresis can be diagnosed with protein stain following acid protein fixation. In addition to the three alleles previously described (C31, C32, C33), a fourth allele (C34) was found. Population data for 25 domestic breeds and Equus przewalskii are presented.     

Monoclonal antibody differentiates chicken A system alloantigens

A monoclonal antibody (ISU-cA) was produced that recognized certain alloantigens of the chicken A blood group locus. Antigens produced by alleles A3, A4 and A8 were positive, and those produced by A2 and A5 were negative, by haemagglutination. The specificity of ISU-cA for chicken A blood group antigens was demonstrated by serologic analyses, genetic crosses and competitive inhibition of binding by anti-A alloantisera. To our knowledge, this is the first reported monoclonal antibody against a chicken blood group alloantigen system other than the B complex.     

Joint report1 of the First International Workshop on Lymphocyte Alloantigens of the Horse held 24–29 October 1981

Six equine lymphocyte alloantigen (ELA) specificities were defined by an international antiserum comparison test and workshop held in 1981. Twelve laboratories from four countries submitted 195 antisera for analysis. The antisera were exchanged among the 12 laboratories and tested in a standard lymphocyte microcytoxicity assay against the isolated lymphocytes at 1009 horses of several breeds. The data was pooled and analysed by a single computer analysis. The calculated χ² values of all cells with all antisera provided comparisons between antisera. Fifteen antisera clusters were formed by this analysis, but only six of these clusters met the criteria established by the workshop for the identification of ELA antigens. No horses of the cell panel positively reacted with more than two of these six specificities. The consensus of the participants, although not substantiated in this workshop, was that these six clusters of antisera define alleles of a single genetic region, the ELA region, and it is likely that this genetic region is the major histocompatibility complex of the horse.     

Preliminary evidence for a fourth allele at the phosphohexose isomerase (Phi) locus of horse erythrocytes

A fourth allele at the horse erythrocyte phosphohexose isomerase (Phi) locus was proposed to account for phenotypes observed after starch gel electrophoresis and enzymatic staining of red cell lysates from American Saddlebred and Tennessee Walking Horse breeds. The gene was rare, having an estimated frequency of 0.009 in 949 Saddlebreds tested.     

Excess of heterozygotes at albumin locus in American Standardbred horses

Summary. Data from 5934 matings of American Standardbred horses provided evidence for an excess of heterozygotes at the albumin locus, statistically significant ( P <0.01) in one mating class (A1-AB stallions x A1-A dams), primarily attributed to an excess of heterozygotes among male offspring.     

Caprine blood groups. 1. The B system

Twelve of 24 monospecific caprine reagents produced by absorption of alloimmune antisera identified a complex blood group system of goats which was designated B, based on the results of a small comparison test with ovine reagents. The frequencies of the 12 B factors differed significantly among the Australian Angora, Texan Angora, Cashmere, and Dairy goat breeds. Three of the antigens detected by the reagents were shown to be related as linear subtypes, designated Ba₁, Ba₂, and Ba₃, and inherited as alleles. The segregations of B factors in 80 sire groups involving 1086 offspring demonstrated that groups of B factors (phenogroups) segregated as products of allelic genes. This work was supported by a grant from the Australian Stud Book, Alison Road, Randwick, New South Wales 2031, Australia.