Joint inheritance of bovine major histocompatibility system antigens W6 and W11

Summary. BOLA workshop antigens W6 and W11 were inherited together in a small number of crossbred Charolais cattle.     

Relationships between the bovine major histocompatibility system and commonly recognized erythrocyte and serum polymorphisms

Linkage at a recombination frequency of 0.10 or less between the bovine major histocompatibility system and the B, C and L red blood cell groups and the albumin, haemoglobin and transferrin loci was excluded by Morton's lod score method. The white blood cell antigen CA19, which is independent of the bovine majar histocompatibility system, is the J blood group.     

Selective forces shaping diversity in the class I region of the major histocompatibility complex in dairy cattle

The major histocompatibility complex (MHC) is one of the most diverse regions of the mammalian genome. Diversity in MHC genes is integral to their function in the immune system, and while pathogens play a key role in shaping this diversity, the contribution of other selective forces remains unclear. The controlled breeding of cattle offers an excellent model for the identification and exploration of these forces. We characterized the MHC class I genes present in a sample of Canadian Holstein A.I. bulls and compared the results with those obtained in an earlier study. No evidence for a reduction in MHC diversity over 20 years was observed, but the relative frequency of some haplotypes had changed: the formerly rare A12 (w12B) haplotype had become the most common, together with A15, while A19, which dominated the earlier sample, had significantly reduced in frequency. Only 7% of bulls in the current study were MHC homozygous compared with the 14% expected under Hardy-Weinberg. To identify the selective forces at work, a gene substitution model was used to calculate the effects of MHC on selection traits using estimated breeding values for each bull. Significant associations between MHC and production, disease and fertility traits were identified, suggesting that MHC diversity is not merely shaped by disease in this controlled breeding system. The decrease in a common haplotype, the reduced number of homozygous bulls and the associations with disease and production traits together indicate that MHC diversity in dairy cattle is maintained by heterozygote advantage.     

Identification of genetic variation in the bovine major histocompatibility complex DRß-like genes using sequenced bovine genomic probes

Two bovine genomic clones that crosshybridize with HLA-DR beta cDNA have been isolated. Nucleotide sequence analysis of the beta 1, beta 2 and transmembrane (TM) exon regions for one of these clones revealed 70, 89 and 86% identity with the corresponding HLA-DR beta exons. Stop codons are present in the beta 1 and TM exons and a single base deletion toward the 3' end of the TM exon negates the consensus sequence for exon/intron splicing. Therefore, we conclude this is a bovine DR beta-like pseudogene, BoDR beta I. Exon-containing regions have been used as probes in Southern blot analyses of bovine genomic DNA digested with EcoRI. The beta 2 exon of BoDR beta I results in prominent bands of 18.9, 7.8, 7.2, 6.4, 5.6, 3.6, 3.0 and 2.7 kb. Polymorphisms were observed for all but the 18.9 kb band and at least three of these bands were identified in each of the 185 animals sampled. A probe containing the TM exon of BoDR beta I hybridizes only to the 5.6- and 3.6-kb bands, suggesting that these are allelic bands corresponding to this pseudogene. Results from hybridizations of a TM exon-containing probe of the second bovine DR beta-like clone (BoDR beta II) suggest that the 6.4- and 2.7-kb bands correspond to this second bovine gene. A nonpolymorphic 8.1-kb band results from a probe containing the BoDR beta I beta 1 exon. Major differences in frequency for the 6.4/2.7 alleles were found for the four breeds sampled.     

Failure to find an association between ocular squamous cell carcinoma and class I antigens of the bovine major histocompatibility system*

Summary. We tested 53 cattle with ocular squamous cell carcinoma (cancer-eye) and 53 paired, matched controls for 25 class I antigens of the bovine major histocompatibility system. The most common antigen was W5 which was present in 40% of the animals with cancer-eye and 36% of the controls. There were no statistically significant differences in BoLA antigen frequency between cattle with and cattle without cancer-eye.     

BoLA antigens are associated with increased frequency of persistent lymphocytosis in bovine leukaemia virus infected cattle and with increased incidence of antibodies to bovine leukaemia virus

The association between bovine major histocompatibility system (BoLA) type and persistent lymphocytosis in cattle with antibodies to bovine leukaemia virus was examined by comparing antigen frequencies in cattle with persistent lymphocytosis to controls matched for age, sex, breed and presence of antibodies to BLV. The cattle came from nine dairy herds in south-east Queensland, Australia; six herds were Australian Illawarra Shorthorn (AIS), two herds were Jersey and one herd was Friesian. Antigen W6 and Eu28R were more common in cattle with persistent lymphocytosis than in controls. Antigen W8 was less common in AIS cattle with persistent lymphocytosis. A study of 24 offspring from one sire, heterozygous for W10 and Eu28R, showed that offspring inheriting Eu28R from the sire were significantly more likely to have antibodies to BLV than offspring inheriting the opposing W10 haplotype.     

Genomic hybridization of bovine class II major histocompatibility genes: 2. Polymorphism of DR genes and linkage disequilibrium in the DQ-DR region

Summary. Class II genes of the bovine major histocompatibility complex have been investigated by Southern blot analysis using human cDNA probes for DQα, DQβ, DRα and DRβ. In this report restriction fragment length polymorphisms of DR α and DR β are described. The polymorphisms were interpreted genetically by analysing five paternal half-sib families of the Swedish Red and White Breed, comprising altogether 28 offspring. Using the restriction enzymes Bam HI, Eco RI and Pvu II, three DRα and three DRβ allelic fragment patterns were resolved. The DR α and DR β genes thus appear to be much less polymorphic than the previously described DQ α and DQ β genes. Also, the observed linkage disequilibrium between DR genes was less pronounced than that between DQ genes, whereas the association between DR and DQ haplotypes was very strong. The family data available indicated strongly that the DQ α, DQ β, DR α and DR β genes are all closely linked.     

Involvement of major histocompatibility complex class I compatibility between dam and calf in the aetiology of bovine retained placenta

The possibility was examined that in cattle compatibility of major histocompatibility complex (MHC) products between dam and calf might negatively influence the placental maturation and expulsion, and therefore increase the risk of retained placenta in healthy, normally calving cattle. Fifteen combinations of a single dam and two offspring were selected; the placenta of the first offspring was normally expelled (control) and the placenta of the second one was retained (case). The MHC class I and class II antigens of the animals were typed by immunoprecipitation and by one-dimensional isoelectric focusing (1D-IEF). Compatibility or incompatibility of class I or class II antigens was established by comparison of the IEF banding patterns of dam and calves. Analysis revealed that MHC class I compatibility between dam and calf increased the risk of retained placenta. In this study, the effect of class II compatibility was not significant, nor was the effect of the interaction of class I and class II. In a subsequent, additional sample the experimental design was extended: induction of tolerance against non-inherited maternal antigens (NIMA) might be implicated in the occurrence of the disorder within the group of class I incompatible cases. In three out of the five class I incompatible retained placenta cases, the banding pattern of the incompatible haplotype of the calf was identical to that of the haplotype of the granddam that was not inherited by the dam (NIMA). Notably, within the nine class I incompatible controls, there were none in which the offspring shared a paternal class I type with the granddam. This might suggest a tolerance-inducing effect of NIMA in cattle in relation to retained placenta.(ABSTRACT TRUNCATED AT 250 WORDS)     

Associations of the bovine major histocompatibility complex DRB3 (BoLA-DRB3) with production traits in Canadian dairy cattle

Associations of two alleles of the bovine major histocompatibility complex DRB3 gene (BoLA-DRB3) with lowered somatic cell score (SCS) and occurrence of disease (BoLA-DRB3.2* 16 and *23, respectively) have previously been documented. The objective of this study was to evaluate potential relationships between BoLA-DRB3 alleles with production traits, namely 305-day milk, milk fat and milk protein yield, in a population of Canadian dairy cattle (Holstein, n = 835 and Jersey, n = 66) over the course of two lactations. No significant associations were detected between BoLA alleles and production traits in Jerseys. In Holsteins, alleles *16 and *23 also did not show associations with production traits but allele *8 was significantly associated with increased 305-day milk, fat and protein yields in the previous lactation (the lactation prior to immunization with a gram negative core antigen vaccine), and with increased protein production in the subsequent (with reference to the time of immunization) lactation. Allele *22 was associated with decreased milk and protein yield in both previous and subsequent lactations. Therefore, it can be concluded that increasing or decreasing the frequency of BoLA alleles *16 and *23 to reduce SCS or increase resistance to mastitis in this population would not have adverse effects on production in this population, and that certain BoLA alleles (*8 and *22) are associated with altered production traits in Canadian Holsteins.