Bovine Major Histocompatibility Complex Research Articles

Genetic variation and responses to vaccines

Disease is a major source of economic loss to the livestock industry. Understanding the role of genetic factors in immune responsiveness and disease resistance should provide new approaches to the control of disease through development of safe synthetic subunit vaccines and breeding for disease resistance. The major histocompatibility complex (MHC) has been an important candidate locus for immune responsiveness studies. However, it is clear that other loci play an important role. Identifying these and quantifying the relative importance of MHC and non-MHC genes should result in new insights into host-pathogen interactions, and information that can be exploited by vaccine designers. The rapidly increasing information available about the bovine genome and the identification of polymorphisms in immune-related genes will offer potential candidates that control immune responses to vaccines. The bovine MHC, BoLA, encodes two distinct isotypes of class II molecules, DR and DQ, and in about half the common haplotypes the DQ genes are duplicated and expressed. DQ molecules are composed of two polymorphic chains whereas DR consists of one polymorphic and one non-polymorphic chain. Although, it is clear that MHC polymorphism is related to immune responsiveness, it is less clear how different allelic and locus products influence the outcome of an immune response in terms of generating protective immunity in outbred animals. A peptide derived from foot-and-mouth disease virus (FMDV) was used as a probe for BoLA class II function. Both DR and DQ are involved in antigen presentation. In an analysis of T-cell clones specific for the peptide, distinct biases to particular restriction elements were observed. In addition inter-haplotype pairings of DQA and DQB molecules produced functional molecules, which greatly increases the numbers of possible restriction elements, compared with the number of genes, particularly in cattle with duplicated DQ genes. In a vaccine trial with several peptides derived from FMDV, BoLA class II DRB3 polymorphisms were correlated with both protection and non-protection. Although variation in immune responsiveness to the FMDV peptide between different individuals is partly explainable by BoLA class II alleles, other genetic factors play an important role. In a quantitative trait locus project, employing a second-generation cross between Charolais and Holstein cattle, significant sire and breed effects were also observed in T-cell, cytokine and antibody responses to the FMDV peptide. These results suggest that both MHC and non-MHC genes play a role in regulating bovine immune traits of relevance to vaccine design. Identifying these genes and quantifying their relative contributions is the subject of further studies.

Chromosomal localization of the major histocompatibility complex in cattle and river buffalo by fluorescent in situ hybridization.

The major histocompatibility complex (MHC) in humans is a polymorphic assemblage of over 70 genes which play key roles in the regulation of the immune response (TROWSDALE et al. 1991). The bovine MHC (bovine lymphocyte antigen, BoLA) was assigned to a rather broad region of cattle chromosome 23 (ql3-23) by sequential Q-banding and isotopic in situ hybridization (FRIES et al. 1986; HEDIGER et al. 1991). In the present study, we use sequential RBA-banding and fluorescent in situ hybridization

Bovine leukocyte antigen major histocompatibility complex class II DRB3*2703 and DRB3*1501 alleles are associated with variation in levels of protection against Theileria parva challenge following immunization with the sporozoite p67 antigen.

Initial laboratory trials of an experimental subunit vaccine against Theileria parva based on the 67-kDa major sporozoite surface antigen revealed a range of responses to challenge. We have analyzed convergence in seven sets of monozygotic twins which suggests that genetic factors may have an influence in determining the degree of protection provided by p67 immunization. In addition, we have examined whether allelic diversity at major histocompatibility complex class II loci influences protection. Analysis of bovine leukocyte antigen DRB3 diversity in 201 animals identified significant associations with vaccine success (DRB3*2703; P = 0.027) and vaccine failure (DRB3*1501; P = 0.013). Furthermore, DRB3*2703 was associated with the likelihood of immunized animals showing little to no clinical signs of disease following challenge. We discuss the acquired and innate immune mechanisms that may be behind the associations described here.

232SEARCH FOR THE BOVINE HOMOLOG OF THE MURINE PED GENE

The aim of the current study was to identify the bovine homolog of the murine Ped (preimplantation embryo development) gene, which regulates mouse preimplantation embryonic growth, including cleavage rate and embryo survivability, and to characterize the expression pattern of this gene during bovine preimplantation embryo development. Experiment (I): The National Center for Biotechnology Information (NCBI) GenBank/EBI EST databases were searched for bovine-expressed sequence tags (EST) that were homologous with the murine Ped gene (Accession number: NM_010394). The resulting ESTs were aligned and assembled in to one complete sequence (841bp), which was shown to be homologous with the Murine Ped gene and the Bovine Major Histocompatibility Complex class I 4221.1 gene (Accession No.: AJ010865, length 1090bp). The expression of the protein product of the Ped gene by bovine tissue was confirmed using Western Blot analysis. Experiment (II): The expression pattern of the Ped gene homolog during in vivo and in vitro bovine preimplantation embryo development was characterized using real time PCR. Embryos at the same stage for age were compared (Day 1: 2-cell; Day 2: 4-cell; Day 3: 8-cell; Day 4: 16-cell; Day 5: early morula;; Day 6, compact/late morula;; Day 7: blastocyst). The relative transcript abundance was consistently lower in the in vitro-cultured embryos at all stages of preimplantation development the differences were significant on Days 2, 4, 5, 6, and 7. The relative transcript abundance was significantly lower on Days 1, 2, and 3 of in vivo culture than on Days 4, 5, 6, and 7 and was significantly higher in Day 7 blastocysts than in Day 5 early morula. In in vitro-cultured embryos the relative transcript abundance was significantly higher in Day 7 blastocysts compared to all other stages of the preimplantation period. Experiment (III): A quantitative analysis of the Ped gene homolog was carried out on replicates of pools of ten 2-cell embryos collected at 25, 28, 32, and >36hpi from three different fertilizations. Transcript relative abundance was highest in those embryos that had cleaved by 25hpi. By 28hpi abundance had decreased slightly;; as time to cleavage increased further to 32 and >36hpi, the relative abundance decreased significantly. In conclusion, we have successfully identified a potential bovine homolog of the murine Ped gene. Furthermore, we have characterized the expression pattern of this gene during preimplantation embryo development in cattle and we have shown that a greater relative abundance of the gene transcript is associated with embryos of higher quality and greater developmental potential.

The diversity of bovine MHC class II DRB3 genes in Japanese Black, Japanese Shorthorn, Jersey and Holstein cattle in Japan

We sequenced exon 2 of the major histocompatibility complex (MHC) class II DRB3 gene from 471 individuals in four different Japanese populations of cattle (201 Japanese Black, 101 Holstein, 100 Japanese Shorthorn, and 69 Jersey cattle) using a new method for sequence-based typing (SBT). We identified the 34 previously reported alleles and four novel alleles. These alleles were 80.0–100.0% identical at the nucleotide level and 77.9–100.0% identical at the amino acid level to the bovine MHC (BoLA)-DRB3 cDNA clone NR1. Among the 38 alleles, eight alleles were found in only one breed in this study. However, these alleles did not form specific clusters on a phylogenetic tree of 236-base pairs (bp) nucleotide sequences. Furthermore, these breeds exhibited similar variations with respect to average frequencies of nucleotides and amino acids, as well as synonymous and non-synonymous substitutions, in all pairwise comparisons of the alleles found in this study. By contrast, analysis of the frequencies of the various BoLA-DRB3 alleles in each breed indicated that DRB3*1101 was the most frequent allele in Holstein cattle (16.8%), DRB3*4501 was the most frequent allele in Jersey cattle (18.1%), DRB3*1201 was the most frequent allele in Japanese Shorthorn cattle (16.0%) and DRB3*1001 was the most frequent allele in Japanese Black cattle (17.4%), indicating that the frequencies of alleles were differed in each breed. In addition, a population tree based on the frequency of BoLA-DRB3 alleles in each breed suggested that Holstein and Japanese Black cattle were the most closely related, and that Jersey cattle were more different from both these breeds than Japanese Shorthorns.

Deletion of one of the duplicated Hsp70 genes causes hereditary myopathy of diaphragmatic muscles in Holstein-Friesian cattle.

Heat-shock protein 70 (Hsp70) is a major chaperone that folds protein and prevents aggregation. The Hsp70 family contains both constitutive and stress-inducible forms. In humans, two of the inducible Hsp70 genes are located within the human major histocompatibility complex (MHC) on 6p21.3, as a duplicated locus, 12 kb apart from each other. We report that loss of one of the duplicated Hsp70 genes, the bovine homologue within the bovine MHC, is responsible for hereditary myopathy of diaphragmatic muscles (HMDM) in Holstein-Friesian cattle. Although the remaining Hsp70 gene is intact, Hsp70 protein levels are dramatically decreased in affected cattle. In normal diaphragmatic muscle, Hsp70 binds several proteins involved in energy metabolism including glycogen phosphorylase (PYGM). Immunohistochemical staining indicated that PYGM accumulated in the HMDM-specific core-like structures in affected cattle. Misfolding of energy-related proteins due to Hsp70 deficiency might lead to protein aggregation and muscle fibre degeneration.

Characterization of naturally processed and presented peptides associated with bovine major histocompatibility complex (BoLA) class II DR molecules.

Differential regulation of genetic resistance to infectious disease may partially be explained by variation in the binding affinity and the repertoire of pathogen-derived antigenic peptides associated with major histocompatibility complex (MHC) molecules. In this study, we investigated characteristics of peptides that bind to the bovine MHC allele BoLA-DRB3*2703, which is associated with occurrence of clinical mastitis in Holstein dairy cattle, and assigned a putative peptide-binding motif to this allele. This was achieved by in vitro expression of allele *2703 as well as a control allele, BoLA-DRB3*1201 which is present at high frequency in Holsteins. Transfected cell lines alone (for allele *1201) or in combination with blood mononuclear cells from an animal homozygous for allele *2703 were used as the source of naturally processed and presented peptides. Subsequent to elution of peptides from BoLA-DR+ cells, their sequences were determined by electrospray ionization mass spectrometry. Eluted peptides were between 13 and 20 amino acids long and the majority were in sets of overlapping sequences. These peptides were derived from intra- and extracellular proteins, as well as foreign proteins present in the culture medium. Some peptides had originated from molecular chaperones present in the endoplasmic reticulum, such as ER-60 and GRP78, pointing to some degree of overlap and cross-sampling between MHC class I and class II antigen presentation pathways. Consistent with reports of human and mouse MHC class II-associated peptides, putative peptide-binding motifs could be assigned to alleles *2703 and *1201, comprising a hydrophobic or an aromatic residue at relative position 1, a hydrophobic residue at position 4 and a small residue at position 6 of the eluted peptides. These findings provide the foundation for future studies of molecular mechanisms of MHC-disease associations of cattle.

Functional expression of a bovine major histocompatibility complex class I gene in transgenic mice

Major histocompatibility complex (MHC) class I restricted cellular immune responses play an important role in immunity to intracellular pathogens. By binding antigenic peptides and presenting them to T cells, class I molecules impose significant selection on the targets of immune responses. Candidate vaccine antigens for cellular immune responses should therefore be analysed in the context of MHC class I antigen presentation. Transgenic mice expressing human MHC (HLA) genes provide a useful model for the identification of potential cytotoxic T lymphocyte (CTL) antigens. To facilitate the analysis of candidate CTL vaccines in cattle, we have produced transgenic mice expressing a common bovine MHC (BoLA) class I allele. The functional BoLA-A11 gene, carried on a 7 kb genomic DNA fragment, was used to make transgenic mice by pronuclear microinjection. Three transgenic mouse lines carrying the BoLA-A11 gene were established. Expression of the BoLA-A11 gene was found in RNA and the A11 product could be detected on the surface of spleen and blood cells. Functional analysis of the A11 transgene product, and its ability to act as an antigen presenting molecules in the mouse host will be discussed.

Functional Organization of MIR2, a Novel Viral Regulator of Selective Endocytosis

Kaposi's sarcoma-associated herpesvirus encodes two related proteins, MIR1 and MIR2, that lead to reduction of the cell surface levels of major histocompatibility complex class I and other polypeptides involved in immune recognition. MIR1 and MIR2 do not affect the assembly or transport of their target proteins through the secretory pathway; rather, they act to enhance the selective endocytosis of target chains from the cell surface. Sequence inspection reveals that the modulator of immune recognition (MIR) proteins contain an NH(2)-terminal zinc finger of the plant homeodomain (PHD) subfamily, two transmembrane (TM) domains, and a C-terminal conserved region (CR). Here we examine the transmembrane topology and functional organization of MIR2. Both the PHD domain and the CR are disposed cytosolically and are essential for MIR-mediated endocytosis. MIR proteins form homo-oligomers; this activity is independent of the PHD and CR elements and maps instead to the TM regions. Analysis of chimeras between MIR1 and MIR2 reveals that the TM regions also mediate target selectivity. Mutations that ablate the PHD or CR regions generate dominant negative phenotypes for major histocompatibility complex class I endocytosis. These findings suggest a domain organization for the MIR proteins, with the TM regions involved in target selection and the cytosolic PHD and CR domains involved in the possible recruitment of cellular machinery that directly or indirectly regulates internalization of target molecules.

Increased expression of major histocompatibility complex (MHC) class I transplantation antigens in bovine trophoblast cells before fusion with maternal cells

The mammalian fetus is potentially at risk from maternal immune attack because it can express paternally inherited polymorphic antigens, including those encoded by the major histocompatibility complex (MHC). The aim of this study was to investigate in more detail MHC class I upregulation by binucleate trophoblast cells in the bovine placenta. A method was developed to isolate binucleate cells by enzymatic disaggregation and density gradient centrifugation of bovine placental cotyledons. In cytospin preparations, 25-30% of purified binucleate cells stained positively with antibodies that recognize bovine MHC class I. The same antibodies were used to immunoprecipitate radiolabelled class I molecules from lysates of binucleate cells and fetal peripheral blood mononuclear cells. The protein species isolated from the two types of cell were similar in size and degree of glycosylation. PCR amplification of cDNA generated from binucleate cells and subsequent sequence analysis demonstrated transcription of MHC class I mRNA species similar to those found in fetal peripheral blood mononuclear cells, and there was no evidence of genetic imprinting of paternally inherited alleles. These results indicate that binucleate cells upregulate expression of MHC class I as they differentiate from MHC-negative uninucleate trophoblast cells. This finding has important implications for the immunological status of the fetus, as binucleate trophoblast cells are destined to cross to the maternal side of the placenta where they fuse with maternal cells. The immunological function of the resulting antigenically mixed fetomaternal hybrid minisyncytia is unknown.

Polymorphism of bovine major histocompatibility complex (MHC) class I genes revealed by polymerase chain reaction (PCR) and restriction enzyme analysis.

The polymorphic exon 2-exon 3 region of bovine major histocompatibility complex (MHC) class I genes was amplified by polymerase chain reaction (PCR) from genomic DNA samples with characterized class I polymorphism. The primers for amplification were designed in conserved regions at the borders of exons 2 and 3, based on all available cDNA sequences. The primers should, therefore, amplify most expressed class I genes, but may also amplify non-expressed class I genes. The PCR amplified class I gene fragments of 700 bp were characterized on the basis of restriction fragment length polymorphism (RFLP). The PCR-RFLP analysis of class I genes showed that the bands in each digestion could be classified as non-polymorphic, as shared between several bovine lymphocyte antigen (BoLA)-A types, or as specific to a single BoLA-A type. The same primers were then used for amplification of class I gene fragments from eight Sahiwal animals, a breed which originated in the Indian subcontinent. These studies showed that BoLA class I PCR-RFLP could be used to study class I polymorphism in family groups.

The use of crossreactive monoclonal antibodies to characterize the immune system of the water buffalo (Bubalus bubalis)

One of the major difficulties in studying the mechanisms of host defense in economically important species indigenous to Asia and the Middle East is the lack of monoclonal antibody (mAb) reagents that define the immune systems of species other than cattle, goats, sheep, and pigs. One strategy that could obviate this problem at minimal cost is to identify existing mAbs that recognize conserved epitopes on orthologous major histocompatibility complex (MHC) and leukocyte differentiation molecules. To explore the potential of this approach, we screened a large set of mAbs that recognize bovine MHC class I and II molecules and leukocyte differentiation molecules to identify mAbs that react with orthologous molecules in water buffalo. One hundred thirty eight were found that recognize conserved determinants on orthologous molecules. In addition to identifying a useful set of reagents, the study has provided insight into the composition of the immune system of the water buffalo (Bubalus bubalis).

Presence of glutamine at position 74 of pocket 4 in the BoLA-DR antigen binding groove is associated with occurrence of clinical mastitis caused by Staphylococcus species

Potential relationships between amino acid motifs in the antigen binding groove of various alleles of the bovine major histocompatibility complex DR (BoLA-DR) molecule and occurrence of clinical mastitis caused by Staphylococcus species (non- Staphylococcus aureus) were investigated in a case-control study. A significant association ( P≤0.05) was detected between the presence of glutamic acid at position β74 and occurrence of mastitis caused by Staphylococcus spp. with a relative risk of 11. This motif is present in BoLA- DRB3.2 ∗ 22, ∗ 23 and ∗ 24 alleles. Presence of a positively charged residue (arginine or lysine) at position 13 also showed a tendency ( P≤0.1) towards an association with a higher risk of clinical mastitis caused by the same bacteria. This motif is present in BoLA- DRB3.2 ∗ 23 and ∗ 8 alleles. Similarly, presence of arginine at position β71 (present in alleles ∗ 23 and ∗ 22) was associated with occurrence of this disease. These positions (β13, β71 and β74) form pocket 4 of the antigen binding groove, which plays an instrumental role in antigen binding and recognition by T-lymphocytes. Thus, it can be concluded that pocket 4 of the BoLA-DR molecule is involved in conferring susceptibility to clinical mastitis caused by Staphylococcus spp.

Standardisation of a procedure for quantifying surface antigens by indirect immunofluorescence

Quantitative indirect immunofluorescence (QIIF) methods used to measure absolute numbers of surface-expressed antigens have produced conflicting results [Marchant, A., Duchow, J., Delville, J., Goldman, M., 1992. Lipopolysaccharide induces up-regulation of CD14 molecule on monocytes in human whole blood. European Journal of Immunology 22, 1663–1665; Antal-Szalmas, P., van Strijp, J.A.G., Weersink, A.J.L., Verhoef, J., van Kessel, K.P.M., 1997. Quantitation of surface CD14 on human monocytes and neutrophils. Journal of Leukocyte Biology 61, 721–728.]. The aim of this study was to standardise a flow cytometric method using the quantitative indirect immunofluorescence kit (QIFIkit, Dako, Denmark) for quantifying surface-expressed bovine classical major histocompatibility complex (MHC) class I molecules. The importance of accurately titrating antibodies in this procedure and using live cell gates is already accepted. However, little work has been carried out in optimising cell washes to remove excess antibody, or to study the influence of cell numbers used in the assay. In addition, information on the binding properties of each antibody is required in order to make accurate measurements. This study demonstrates that a number of critical parameters must be established prior to using this method for accurate numerical assessment of cell surface-expressed molecules.

Fine-Mapping of a Region of Variation in Recombination Rate on BTA23 to the D23S22–D23S23 Interval Using Sperm Typing and Meiotic Breakpoint Analysis

Meiotic recombination rate (θ) within chromosome segments of similar physical size is known to vary widely throughout the genome. This variation has a genetic component, occurring between the sexes and among individuals of the same sex. We reported previously the existence of variation in θ between males in the DYA–PRL interval on bovine chromosome 23 (BTA23). This region contains the bovine major histocompatibility complex and has been shown to contain recombination hotspots in humans and mice. The aim of this study was to map more finely the interval(s) on BTA23 where variation in θ occurs using sperm typing and meiotic breakpoint analysis. By adding a marker (DRB3) between DYA and PRL, the DYA–PRL interval was subdivided into two adjacent intervals, thus permitting evaluation and comparison of θ among five bulls. Significant variation in θ was found for both intervals; θDYA–DRB3 ranged from 13.2 to 28.1%, and θDRB3–PRL ranged from 2.4 to 13.0%. The variation in θ was individual- and region-specific. A meiotic breakpoint strategy employing PCR amplification products from recombinant sperm was then used to refine the chromosomal location associated with variation in θ within the DYA–DRB3 interval. The subinterval D23S22–D23S23 exhibited the greatest degree of variation among bulls having high and low θ within the DYA–DRB3 interval. To confirm this result, θD23S22–D23S23 was directly evaluated in three additional randomly chosen bulls using sperm typing. The region showing variation in θ was narrowed to the D23S22–D23S23 subinterval, ranging from 4.6 to 9.2%. Identification of the molecular basis for variation in θ may be useful for map-dependent applications, such as marker-assisted selection and positional cloning of genes affecting physiologically important traits.

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.

Cattle MHC: evolution in action?

Because major histocompatibility complex (MHC) genes play a major role in the development of acquired immune responses, it is essential to obtain comparative information on their organisation, expression and possible functional dichotomies in different species. In human, three classical, polymorphic class I genes (HLA-A, B- and -C) and four expressed A/B class II gene pairs (HLA-DM, -DP, -DQ and -DR) are each present on all haplotypes. With the exception of the HLA-DRB loci, it has been assumed that a similar rigid organisational situation exists in other mammalian species. However, extensive analysis of the bovine MHC (BoLA) at both the genomic and transcriptional levels has revealed a degree of genetic fluidity not described in other species. None of the four (or more) classical class I genes identified is consistently expressed, and haplotypes differ from one another in both the number and composition of expressed class I genes. Similarly, in the class II region, the number of DQ genes varies between haplotypes in both number and composition. These variations in both class I and II (which appear to reflect differences at the genomic level) are likely to play an important role in cattle immune responses. The observed phenotypic differences in cattle demonstrate very clearly the dynamic nature of the MHC region. This review addresses the functional impact of such variation in different breeds and populations, and its significance in terms of MHC evolution.

Alteration of leukocyte populations in calves concurrently infected with bovine respiratory syncytial virus and bovine viral diarrhea virus.

Bovine viral diarrhea virus (BVDV) infection altered leukocyte populations in calves that were reflected by depression of T, BoCD4+, and BoCD8+ lymphocytes in the thymus and depression of B lymphocytes in Peyer's patches (PP). The present study was based on mononuclear leukocyte preparations from eighteen 9- to 12-month-old crossbred calves that were each exposed to either bovine respiratory syncytial virus (BRSV), BVDV, or BRSV and BVDV concurrently, or served as mock-infected controls. Peripheral blood leukocytes were collected on postinfection days (PID) 0, 2, 4, 6, and 8, and cell populations from thymus, spleen, mesenteric lymph node, and PP were collected at necropsy on PID 9. The leukocytes were analyzed using flow cytometry for lymphocyte subpopulations expressing antigens specific for BoCD2, BoCD4, BoCD8, BoWC1, lambda light chain of bovine immunoglobulin, BoCD11b and major histocompatibility complex (MHC) class II. Concurrent BRSV and BVDV infections caused exaggerated alterations in leukocyte populations with a greater percentage of T-lymphocytes harvested from the PP. Alterations in the leukocyte populations in lymphatic tissues and in peripheral circulation due to BVDV infection may be an important mechanism for causation of clinically severe diseases of the respiratory and digestive tracts during concurrent BRSV and BVDV infections.

Physical assignment of the bovine MHC class IIa and class IIb genes

Screening of a bovine yeast artificial chromosome (YAC) library revealed two clones which contain most of the class II genes of the major histocompatibility complex (MHC) known to date. The YACs were mapped by fluorescence in situ hybridization (FISH) and characterized for the class II genes they contain. We found that the classic class II genes BoLA- DQA, -DQB, -DRA, and -DRB3 are located at BTA 23q21 and the non-classic class II genes DYA, DIB, LMP2, LMP7, TAP2, BoLA-DOB, -DMA, -DMB, and -DNA are located at BTA 23q12→q13. These two different mapping locations confirm and extend previous findings of a gross physical distance between classic and non-classic MHC class II genes in cattle.

Seasonal variations of diet composition in farmland field mice Apodemus spp. and bank voles Clethrionomys glareolus

Polymerase chain reaction (PCR) primers specific to exon 2 of the bovine Major Histocompatibility Complex (MHC) class II gene BoLA-DRB3 were used to amplify the homologous region (284bp) in 21 European bison Bison bonasus (Linnaeus, 1758).