Polymorphism of the CD4 and CD5 differentiation antigens in cattle

A polymorphic CD4 epitope related to increased susceptibility to Babesia bovis in Canchim calves

Different allelic forms of bovine CD4 were previously described in cattle and were also observed in Canchim calves examined in the present experiment. However, the functional relevance of these different CD4 phenotypes has not yet been investigated. CD4 + T helper cells are known to play a central role in immune control against Babesia bovis infection. Thus, our study aimed to compare the profiles of immune cells, specific antibody titers and blood infection levels measured by qPCR (quantitative polymerase chain reaction) in calves naturally infected with B. bovis, phenotyped as CD4- (absence of anti-CD4 staining), CD4 + (intermediate staining) or CD4 ++ (high staining). The CD4 mRNA precursor was also measured in these animals. Calves with the CD4- phenotype showed higher amounts of B. bovis DNA in blood samples, compared to the other CD4 phenotypes. It was also observed that these calves with higher levels of infection had lower amounts of natural killer cells and higher expression of the CD4 gene, which can be interpreted as a compensation for the failure of the altered CD4 receptor to recognize relevant B. bovis epitopes.

Cross-reactivity of mAbs to human CD antigens with cells from cattle

A panel of 377 commercially available mAbs were submitted to the animal homologue section of the 8th International Workshop on Human Leukocyte Differentiation Antigens (HLDA8, Adelaide, Australia) for cross-reactivity studies on different animal species. In this study we describe the results of testing the mAbs on cattle cells by flow cytometry and Western blot. Eight commercial suppliers participated, providing mAbs to a total of 144 CD antigens plus controls. Fifty-two mAbs were identified as potentially staining cattle cells in the first round screen. In the second phase, 38 mAbs were confirmed as staining cattle cells. This included some that may recognise polymorphic determinants and others with atypical distribution patterns compared to humans. mAb to human CD9, CD11a, CD14, CD18, CD21, CD23, CD29, CD44, CD45R, CD47, CD49d and CD172a cross-reacted with bovine cells and mAb to CD22, CD88, CD119 and CD163 stained CD antigens that have not previously been identified in cattle.

Identification of two allelic forms of ovine CD4 exhibiting a Ser183/Pro183 polymorphism in the coding sequence of domain 3

The ovine CD4 cDNA sequence from four sheep sources (Australian Merino, Indonesian Thin Tail, Canadian cross bred, Prealpes du sud) predicts a protein of 455 residues with position 130 in the V2 domain exhibiting a W instead of C suggesting that, like the white whale, dog and cat sequences, sheep CD4 contains only two disulphide bonds. The sequence shows 73% amino acid identity and 83% nucleotide identity to a CD4 sequence from the white whale and significant identity to a partial sequence (314 residues) of bovine CD4 (87% amino acid identity, 93% nucleotide identity). Phylogenetic analysis showed that the ovine CD4 sequence forms a clade with the pig, white whale, dolphin, dog and cat CD4. Two forms of ovine CD4 were identified which differ by a single base pair (T/C) in their cDNA sequence at position 622. This polymorphism is also present in sheep genomic DNA in Hardy-Weinberg equilibrium, suggesting that at least two alleles of CD4 exist in the ovine genome with no selection for a particular allele. This polymorphism changes the first codon position of amino acid 183 and results in a Pro/Ser substitution in the N-terminal region of domain 3 of the CD4 protein.

Depletion of bovine CD8+ T cells with chCC63, a chimaeric mouse-bovine antibody

In order to investigate the role of T cells in immune responses to infectious pathogens, depletion of individual T cell subsets using monoclonal antibodies (mAbs) is commonly undertaken. Since most mAbs are of murine origin, such depletion studies in cattle are restricted by the bovine anti-mouse antibody (BAMA) response to the mouse mAbs used for the depletions. In this study, we describe the use of antibody engineering to overcome the BAMA response. The variable region cDNA from CC63, a monoclonal mouse anti-bovine CD8 antibody, has been expressed in conjunction with bovine constant region genes to produce a mouse-bovine chimaeric antibody (chCC63). Characterisation of chCC63 showed that the antibody contained a bovine constant region and specifically bound bovine CD8+ T cells. Furthermore, chCC63 blocked the binding of the original mouse antibody, CC63, and mediated complement-dependent lysis of bovine CD8+ cells in vitro. In vivo, chCC63 depleted calves of CD8+ T cells as effectively as CC63 and provoked a BAMA response that was about one-tenth of that seen with the mouse antibody.

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.

The Ly-1.1 and Ly-1.2 epitopes of murine CD5 map to the membrane distal scavenger receptor cysteine-rich domain

CD5 is a member of a superfamily of proteins which contain one or more extracellular domains homologous to the type I macrophage Scavenger Receptor cysteine-rich (SRCR) domain. The extracellular region of CD5 is composed of three SRCR domains (D1, D2, D3). Murine CD5 (mCD5) is polymorphic (Ly-1.1 and Ly-1.2 alleles), however, the only murine CD5 gene characterized to date encodes the Ly-1.2 allele (mCD5.2). Likewise, the domain specificity of many of the available anti-mCD5 mAb recognizing either Ly-1.1 or Ly-1.2 or both has not been examined. Herein we describe the isolation and characterization of cDNA encoding the Ly1.1 allele (mCD5.1) and map the location and molecular nature of the mCD5 allelic variation. We also determined which SRCR domain of mCD5 is recognized by a panel of anti-mCD5 mAb. The mCD5.1 protein differs from mCD5.2 in only three amino acids, all of which map to the most amino terminal SRCR domain (D1) of mCD5. An additional seven silent substitutions were observed in the nucleotide sequence encoding mCD5 D1, D2 and transmembrane domains. Immunoglobulin (Ig) fusion proteins consisting of various combinations of mCD5.1 or mCD5.2 SRCR domains were produced and used to determine that allele specific mAb bound to D1, confirming sequence data. MAb against monomorphic determinants on mCD5 bound to each mCD5D11g.

Cluster analysis

Cluster analysis was performed on flow cytometry data generated from the reactivities of the 302 workshop monoclonal antibodies with 36 target cell preparations. The antibodies were assigned to 42 preliminary clusters that were subjected to further examination in subsequent stages of the workshop.

Reactivity of workshop antibodies on L cell and COS cell transfectants expressing bovine CD antigens

Mouse L cells and COS cells were transfected with either genomic DNA or cDNAs encoding leukocyte differentiation antigens. Positive transfectants were isolated by FACS and cloned by limiting dilution. Transfectants expressing CD4, CD5, CD8, CD25, CD44, two different WC1 gene products and a transfectant expressing an unknown gene product were isolated using these techniques. Antibodies from the various preliminary clusters were analysed for reactivity on these transfectants. The results confirm the fine specificity of mAbs for two alleles of CD4 and CD5; they also subdivide mAbs recognizing CD8 into two groups based on their specificity for the CD8 alpha chain or a combination of both alpha and beta chains. The data also provides support for the clustering of mAbs recognizing CD25 and CD44 based on transfection of cDNAs encoding these specificities. These results reflect the ability of transfection technology to elucidate the fine specificity of mAbs recognizing bovine CD antigens.