Molecular cloning of bovine CD14 gene

CD4 and MHCII phenotypic variability of peripheral blood monocytes in dogs

In humans and mice, the detailed phenotypic and functional characterization of peripheral blood monocytes allows for identification of three monocyte subsets. There are also evidences of monocyte phenotypic heterogeneity in other species, including cattle, sheep, pig and horse. However, little is known about such variability in dogs. The aim of the study was to determine whether and how peripheral blood monocytes of healthy dogs differ in the presence of MHCII and CD4 and in the basal production of reactive oxygen species (ROS). Three distinct subsets of CD11b+CD14+ monocytes were found in peripheral blood samples of healthy dogs, based on the variations in the density of MHCII and CD4 surface molecules: MHCII+CD4- (Mo1), MHCII+CD4+ (Mo2) and MHCII-CD4+ (Mo3). The Mo2 and Mo3 were significantly lower in percentage than Mo1 but their basal ROS production was higher. Within the Mo2 and Mo3 subsets, the percentage of cells producing ROS was significantly higher comparing to cells lacking this activity. Canine peripheral blood monocytes vary in the expression of MHCII and CD4 and in the activity suggesting that cells within the three identified subsets carry out different functions. The higher production of ROS in non-activated cells within small subsets of Mo2 and Mo3 monocytes might indicate their immunomodulatory potential.

Molecular Characterization and SNP Detection of CD14 Gene of Crossbred Cattle

CD14 is an important molecule for innate immunity that can act against a wide range of pathogens. The present paper has characterized CD14 gene of crossbred (CB) cattle (Bos indicus×Bos taurus). Cloning and sequence analysis of CD14 cDNA revealed 1119 nucleotide long open reading frame encoding 373 amino acids protein and 20 amino acids signal peptide. CB cattle CD14 gene exhibited a high percentage of nucleotide identity (59.3–98.1%) with the corresponding mammalian homologs. Cattle and buffalo appear to have diverged from a common ancestor in phylogenetic analysis. 25 SNPs with 17 amino acid changes were newly reported and the site for mutational hot-spot was detected in CB cattle CD14 gene. Non-synonymous substitutions exceeding synonymous substitutions indicate the evolution of this protein through positive selection among domestic animals. Predicted protein structures obtained from deduced amino acid sequence indicated CB cattle CD14 molecule to be a receptor with horse shoe-shaped structure. The sites for LPS binding, LPS signalling, leucine-rich repeats, putative N-linked glycosylation, O-linked glycosylation, glycosyl phosphatidyl inositol anchor, disulphide bridges, alpha helix, beta strand, leucine rich nuclear export signal, leucine zipper and domain linker were predicted. Most of leucine and cysteine residues remain conserved across the species.

Chicken CD14, unlike mammalian CD14, is trans-membrane rather than GPI-anchored

A cDNA encoding the chicken homologue of the human myelomonocytic differentiation antigen, CD14, was cloned by RT-PCR from chicken bone marrow cell RNA, using oligonucleotide primers based on the predicted cDNA sequence. The cloned chicken CD14 (chCD14) cDNA encodes an open reading frame of 465 amino acids (aa), with 31-34% aa identity to mouse, bovine and human (hu) CD14. As in mouse and man, chCD14 is a leucine-rich protein. In mammals, CD14 is a GPI-anchored protein. Protein structure analysis suggested that chCD14, by contrast, was potentially a trans-membrane protein. The predicted aa sequence comprises an extracellular domain of 417 aa, followed by a 23-aa trans-membrane segment, and a 25-aa intracytoplasmic region, the latter containing no obvious signalling motifs. COS-7 cells were transfected with p3XFLAG-CMV-8::chCD14 or pCDM8::huCD14, incubated with or without PI-PLC and stained with anti-FLAG or anti-huCD14 antibody respectively. PI-PLC cleaved huCD14 but not chCD14, suggesting that chCD14 is not GPI-anchored. Real-time quantitative RT-PCR analysis revealed that chCD14 mRNA was expressed in most lymphoid and non-lymphoid tissues, except muscle. ChCD14 mRNA was also expressed in most cells examined but strongly expressed in chicken peripheral blood monocyte/macrophages and KUL01+ splenocytes.

Bovine CD14 gene characterization and relationship between polymorphisms and surface expression on monocytes and polymorphonuclear neutrophils

Background

CD14 is an important player in host innate immunity in that it confers lipopolysaccharide sensitivity to cell types like neutrophils, monocytes and macrophages. The study was aimed at characterizing the CD14 gene of cattle for sequence variations and to determine the effect of variations on the expression of the protein on the surfaces of monocytes and neutrophils in healthy dairy cows.

Results

Five SNPs were identified: two within the coding regions (g.A1908G and g.A2318G, numbering is according to GenBank No. EU148609), one in the 5' (g.C1291T) and two in the 3' (g.A2601G and g.G2621T) untranslated regions. SNP 1908 changes amino acid 175 of the protein (p.Asn175Asp, numbering is according to GenBank No. ABV68569), while SNP 2318 involves a synonymous codon change. Coding region SNPs characterized three gene alleles A (GenBank No. EU148609), A₁ (GenBank No. EU148610) and B (GenBank No. EU148611) and two deduced protein variants A (ABV68569 and ABV68570) and B (ABV68571). Protein variant A is more common in the breeds analyzed. All SNPs gave rise to 3 haplotypes for the breeds. SNP genotype 1908AG was significantly (P < 0.01) associated with a higher percentage of neutrophils expressing more CD14 molecules on their surfaces. The promoter region contains several transcription factor binding sites, including multiple AP-1 and SP1 sites and there is a high conservation of amino acid residues between the proteins of closely related species.

Conclusion

The study has provided information on sequence variations within the CD14 gene and proteins of cattle. The SNP responsible for an amino acid exchange may play an important role in the expression of CD14 on the surfaces of neutrophils. Further observations involving a larger sample size are required to validate our findings. Our SNP and association analyses have provided baseline information that may be used at defining the role of CD14 in mediating bacterial infections. The computational analysis on the promoter and comparative analysis with other species has revealed regions of regulatory element motifs that may indicate important regulatory effects on the gene.

CD14: a soluble pattern recognition receptor in milk

An innate immune system capable of distinguishing among self, non-self, and danger is a prerequisite for health. Upon antigenic challenge, pattern recognition receptors (PRRs), such as the Toll-like receptor (TLR) family of proteins, enable this system to recognize and interact with a number of microbial components and endogenous host proteins. In the healthy host, such interactions culminate in tolerance to self-antigen, dietary antigen, and commensal microorganisms but in protection against pathogenic attack. This duality implies tightly regulated control mechanisms that are not expected of the inexperienced neonatal immune system. Indeed, the increased susceptibility of newborn infants to infection and to certain allergens suggests that the capacity to handle certain antigenic challenges is not inherent. The observation that breast-fed infants experience a lower incidence of infections, inflammation, and allergies than formula-fed infants suggests that exogenous factors in milk may play a regulatory role. There is increasing evidence to suggest that upon exposure to antigen, breast milk educates the neonatal immune system in the decision-making processes underlying the immune response to microbes. Breast milk contains a multitude of factors such as immunoglobulins, glycoproteins, glycolipids, and antimicrobial peptides that, qualitatively or quantitatively, may modulate how neonatal cells perceive and respond to microbial components. The specific role of several of these factors is highlighted in other chapters in this book. However, an emerging concept is that breast milk influences the neonatal immune system's perception of "danger." Here we discuss how CD14, a soluble PRR in milk, may contribute to this education.

Molecular cloning, mapping, and tissue expression of the porcine cluster of differentiation 14 (CD14) gene

CD14 plays an important role in initiating the innate response to lipopolysaccharide from Gram-negative bacteria. The gene and corresponding cDNA of porcine CD14 were sequenced and characterized. The porcine CD14 gene consists of two exons and a short intron (80 bp) located immediately after the ATG translation start codon. This structure is very similar to the CD14 gene of human, rat, mouse, rabbit, horse, and cow. The sequence of the porcine CD14 protein is 59-76% identical to that of rat, mouse, rabbit, human, horse, and cow CD14 protein. A highly conserved structure of the CD14 protein with respect to the leucine-rich repeats domain and the N-glycosylation sites was observed between species. Porcine CD14 was assigned to porcine chromosome 2q21 by a radiation hybrid panel. Using RT-PCR analysis, porcine CD14 transcripts were detected in liver, spleen, thymus, white matter, and skeletal muscle.

Cloning, characterization and mapping of porcine CD14 reveals a high conservation of mammalian CD14 structure, expression and locus organization

The cell surface protein CD14 plays a central role in innate immunity as a pattern recognition receptor. CD14 is part of a receptor complex also including toll-like receptor 4 and MD2 proteins. Binding of the ligand lipopolysaccharide to the complex on myeloid cells leads to release of pro-inflammatory cytokines and mediators from the cell. In this study, we present the cloning, characterization and tissue expression pattern of a porcine CD14 encoding cDNA, and the chromosomal localization of the porcine CD14 gene. The open reading frame is predicted to encode a protein of 373 amino acids, which shows conservation of structural as well as functional regions when compared to other mammalian species. The CD14 gene was localized to porcine chromosome 2 in a region syntenic to human chromosome 5q. Transcription analysis shows that CD14 is widely expressed in tissues examined in this study, which correlates well with expression primarily on myeloid cells.

Molecular cloning, chromosomal location, and expression analysis of porcine CD14

CD14 is a membrane-associated glycosylphosphatidylinositol (GPI)-anchored protein that binds lipopolysaccharide (LPS) of Gram-negative bacteria and enables LPS-dependent responses in a variety of cells. In this study a cDNA containing the porcine CD14 coding sequence has been cloned and its complete sequence determined. The amino acid sequence deduced from pig CD14 cDNA encodes a 373 amino acid polypeptide that exhibits 75%, 72%, 69%, 66%, 57% and 56% similarity to CD14 from cow, horse, human, rabbit, mouse and rat, respectively. Structural analysis showed that the porcine CD14 is a membrane glycoprotein with a GPI-anchor site and an extracellular domain containing 11 leucine-rich repeats. In addition, the LPS-binding regions identified in the human CD14 are highly conserved in the N-terminal domain of the porcine sequence. Fluorescence in situ hybridization was used to locate the CD14 gene on the pig chromosome 2, band q28. Expression analysis revealed that porcine CD14 transcripts were detected in all tissues and cells examined, suggesting that the expression of porcine CD14 gene is not restricted to myeloid cell lineage. Finally, we report that LPS stimulation significantly up-regulated CD14 gene expression in porcine alveolar macrophages.