Bovine Major Histocompatibility Complex Class Research Articles

A new method for typing bovine major histocompatibility complex class II DRB3 alleles by combining two established PCR sequence‐based techniques

Recently, two polymerase chain reaction sequence-based typing (PCR-SBT) methods were reported for the genotyping of the bovine leukocyte antigen (BoLA)-DRB3. One technique is a single PCR-SBT (sPCR-SBT) method that generates heterozygous sequences that are subsequently analyzed by the haplofinder program, while the other technique is a nested PCR-SBT (nPCR-SBT) method that allows the analysis of heterozygous sequences using the assign 400ATF software. In this study, these techniques were compared and then integrated to produce an improved genotyping method. The primer set used for sPCR-SBT was more accurate than those used for nPCR-SBT. Combining sPCR-SBT with the assign 400ATF software previously reported for nPCR-SBT enables rapid and accurate genotyping of a large number of DNA samples.

Two Distinct Conformations of a Rinderpest Virus Epitope Presented by Bovine Major Histocompatibility Complex Class I N*01801: a Host Strategy To Present Featured Peptides

The presentation of viral peptide epitopes to host cytotoxic T lymphocytes (CTLs) is crucial for adaptive cellular immunity to clear the virus infection, especially for some chronic viral infections. Indeed, hosts have developed effective strategies to achieve this goal. The ideal scenario would be that the peptide epitopes stimulate a broad spectrum of CTL responses with diversified T-cell receptor (TCR) usage (the TCR repertoire). It is believed that a diversified TCR repertoire requires a "featured" peptide to be presented by the host major histocompatibility complex (MHC). A featured peptide can be processed and presented in a number of ways. Here, using the X-ray diffraction method, the crystal structures of an antigenic peptide derived from rinderpest virus presented by bovine MHC class I N*01801 (BoLA-A11) have been solved, and two distinct conformations of the presented peptide are clearly displayed. A detailed analysis of the structure and comparative sequences revealed that the polymorphic amino acid isoleucine 73 (Ile73) is extremely flexible, allowing the MHC groove to adopt different conformations to accommodate the rinderpest virus peptide. This makes the peptide more featured by exposing different amino acids for T-cell recognition. The crystal structures also demonstrated that the N*01801 molecule has an unusually large A pocket, resulting in the special conformation of the P1 residue at the N terminus of the peptide. We propose that this strategy of host peptide presentation might be beneficial for creating a diversified TCR repertoire, which is important for a more-effective CTL response.

Regulation of a Bovine Nonclassical Major Histocompatibility Complex Class I Gene Promoter1

Studies have shown in humans and other species that the major histocompatibility complex class I (MHC-I) region is involved at a number of levels in the establishment and maintenance of pregnancy. The aim of this study was to characterize how a bovine nonclassical MHC-I gene (NC1) is regulated. Initial serial deletion experiments of a 2-kb fragment of the NC1 promoter identified regions with positive regulatory elements in the proximal promoter and evidence for a silencer module(s) further upstream that cooperatively contributed to constitutive NC1 expression. The cytokines interferon tau (IFNT), interferon gamma (IFNG), and interleukin 4 (IL4) significantly increased luciferase expression in NC1 promoter reporter constructs and endogenous NC1 mRNA levels in a bovine endometrial cell line. In addition, IFNG, IL3, IL4, and progesterone significantly increased Day 7 bovine blastocyst NC1 mRNA expression when supplemented during in vitro embryo culture. Site-directed mutagenesis analysis identified a STAT6 binding site that conferred IL4 responsiveness in the NC1 proximal promoter. Furthermore, methylation treatment of the proximal promoter, which contains a CpG island, completely abrogated constitutive NC1 expression. Overall, the findings presented here suggest that constitutive NC1 expression is regulated positively by elements in the proximal promoter, which are further controlled by upstream silencer modules. The promoter is responsive to IFNT, IFNG, and IL4, suggesting possible roles for these cytokines in bovine preimplantation embryo survival and/or maternal-fetal tolerance. Our studies also suggest that methylation of the proximal promoter, in particular, could play a significant role in regulating NC1 expression.

Characterization of the Non-Classical Major Histocompatibility Complex Class-I Gene (NC1) Promoter in a Bovine Endometrial Cell Line.

Studies have shown that the majority of fetal and embryonic loss in cattle occurs in the first 16 days post fertilization. The regulation of class I major histocompatibility complex (MHC) expression is critical to the establishment and maintenance of pregnancy, however, very little is known about how this occurs in cattle. We investigated one of the four bovine non-classical MHC class I genes (NC1) [http://www.ebi.ac.uk/ipd/mhc/bola/]. Our specific aim was to characterize how the promoter of NC1 is regulated. Initial bioinformatic analysis identified putative transcription factor binding sites and transcription start sites within the NC1 promoter. Subsequently, the proximal (340bp) and extended promoter fragments (1.9kb) of the NC1 gene were amplified from Holstein Friesian genomic DNA and cloned into the luciferase reporter vector (pGL4.17). Bovine endometrial cells (BEND) were transiently co-transfected with the promoter constructs and a Renilla control vector (pGL4.74). Promoter activity was then established in the presence of various MHC-I regulators including cytokines and growth factors. To date, we have shown that the NC1 promoter initiates transcription in the BEND cell line. Notably, both IL-4 and IFN-γ significantly increased luciferase expression in both the proximal and extended NC1 promoter constructs. A likely candidate for the IL-4 responsiveness is a STAT6 binding site present in the 340bp NC1 promoter construct. In addition, the luciferase expression value was consistently lower for the 1.9kb fragment relative to the 340bp fragment, suggesting the presence of an active silencer site. This possibility was investigated further using serial deletion analysis; a series of seven luciferase NC1 promoter constructs (extending from 110bp to the longest 1.9kb fragment) were generated and analyzed. Positive regulatory elements were detected from 203bp to 652bp upstream of the transcription start site. Likely candidates for the positive regulatory effects and for the largest contribution to constitutive NC1 expression are enhancer A and the GC box. However further downstream from these sites, we detected evidence of a silencer module (from -1 to -1.9kb) in the NC1 promoter. In conclusion, our findings suggest potential roles for both IL-4 and IFN-γ in the regulation of the bovine NC1 gene. Furthermore, key regions within the NC1 promoter have been identified as having either a positive or negative effect on NC1 expression. These regions are expected to tightly regulate both the constitutive and induced expression patterns of the NC1 gene in a co-operative manner. Research supported by SFI-PICA Program, Grant code B813 (poster)

Distribution and origin of bovine major histocompatibility complex class II DQA1 genes in Japan

We sequenced the major histocompatibility complex (MHC) class II DQA1 gene in 352 Japanese cattle (95 Japanese Black, 91 Holstein, 102 Japanese Shorthorn and 64 Jersey cattle) using a new sequence-based typing method. In total, 19 bovine MHC (BoLA)-DQA1 alleles, of which two were novel alleles, were detected. The Holstein, Jersey, Japanese Shorthorn and Japanese Black breeds had 13, 12, 10 and 15 alleles, respectively. The dendrogram that was constructed by the neighbor-joining method on the basis of the DQA1 gene allele frequencies of the four Japanese cattle breeds showed that the Holstein and Japanese Black breeds were closest to each other, with Jersey being farther from these two breeds than Japanese Shorthorn. In addition, Wu-Kabat analysis showed that the DQA1 alleles of the Holstein and Japanese Black were the most and least polymorphic, respectively. Phylogenetic analyses indicated that the DQA1 gene of Bovidae such as cattle, sheep, bison and goat were more similar to pig SLA-DQA genes than to human HLA-DQA1 and dog DLA-DQA genes. The cattle, goat, bison, sheep, human and pig DQA1 molecules had similar rates of amino acid sequence polymorphism, but the distribution of their polymorphic residues differed from that in the dog DQA1 protein. However, the Bovidae DQA1 molecule had more polymorphic residues than the human, pig and dog DQA molecules at two regions, namely positions 52-53 and 65-66. This indicates that the Bovidae DQA1 locus is more polymorphic than the DQA loci of other species.

Sequence Analysis of Goat Major Histocompatibility Complex Class I Genes

The polymorphism of major histocompatibility complex (MHC) class I genes has been often involved in the resistance/susceptibility to a variety of infectious and parasitic diseases. In this work, the complete sequence of the coding region of a major histocompatibility complex (MHC) class I gene in goats (Cahi-N*01701, GenBank accession no. EF569216) is reported. The length of the corresponding open reading frame was 1,077 bp encoding a mature protein of 337 amino acids. Sequencing of additional clones allowed us to identify a second locus (Cahi-NC4*50301, GenBank accession no. EF569217) that, after performing a Bayesian phylogenetic analysis, happened to cluster with a bovine non-classical MHC class I gene. Nonclassical MHC class I molecules display low levels of polymorphism and fulfill an important immunoregulatory role in the placenta to inhibit maternal rejection. This initial description of the gene content of the goat MHC class I region will contribute to the characterization, in this ruminant species, of one of the most important genetic factors in the elicitation of innate and adaptive immune responses against pathogens.

Association of the bovine leukocyte antigen major histocompatibility complex class II DRB3*4401 allele with host resistance to the Lone Star tick, Amblyomma americanum

The MHC of cattle, known as the bovine leukocyte antigen (BoLA) complex, plays an integral role in disease and parasite susceptibility, and immune responsiveness of the host. While susceptibility to tick infestation in cattle is believed to be heritable, genes that may be responsible for the manifestation of this phenotype remain elusive. In an effort to analyze the role that genes within the BoLA complex may play in host resistance to ticks, we have evaluated components of this system within a herd of cattle established at our laboratory that has been phenotyped for ectoparasite susceptibility. Of three microsatellite loci within the BoLA complex analyzed, alleles of two microsatellite loci within the BoLA class IIa cluster (DRB1-118 and DRB3-174) associated with the tick-resistant phenotype, prompting further investigation of gene sequences within the DRB3 region. DRB3 is a class IIa gene, the second exon of which is highly polymorphic since it encodes the antigen recognition site of the DR class II molecule. Analysis of the second exon of the DRB3 gene from the phenotyped calves in our herd revealed a significant association between the DRB3*4401 allele and the tick-resistant phenotype. To our knowledge, this is the first report of a putative association between a class IIa DRB3 sequence and host resistance to the Lone Star tick. Elucidation of the mechanism involved in tick resistance will contribute to improving breeding schemes for parasite resistance, which will be beneficial to the cattle industry.

Polymorphism of exon 2-3 of bovine major histocompatibility complex class I BoLa-A gene

The exon 2-3 region of bovine major histocompatibility complex (MHC) class I BoLa-A gene was investigated for polymorphisms in three breeds of cattle originated in the Indian subcontinent namely Sahiwal, Tharparkar, Hariana, as well as crossbred (Bos taurus x Bos indicus) cattle and Jersey, the exotic breed (Bos taurus). The PCR amplified fragment of 714 bp showed distinct DdeI-, TaqI- and HinfI- RFLP patterns, thus confirming a higher degree of polymorphism in this region. To our knowledge this is the first report of HinfI restriction patterns for BoLa-A exon 2-3. The sequencing results revealed a number of nucleotide substitutions in this region, which resulted in amino acid changes. The present investigation confirmed that MHC class I BoLa-A exon 2-3 is highly polymorphic in cattle.

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.

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.

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).

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.

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).