N-Glycosylation influences the structure and self-association abilities of recombinant nucleolin.

Nucleolin is a major nucleolar protein involved in fundamental processes of ribosome biogenesis, regulation of cell proliferation and growth. Nucleolin is known to shuttle between nucleus, cytoplasm and cell surface. We have previously found that nucleolin undergoes complex N- and O-glycosylations in extra-nuclear isoforms. We found that surface nucleolin is exclusively glycosylated and that N-glycosylation is required for its expression on the cells. Interestingly, the two N-glycans are located in the RNA-binding domains (RBDs) which participate in the self-association properties of nucleolin. We hypothesized that the occupancy of RBDs by N-glycans plays a role in these self-association properties. Here, owing to the inability to quantitatively produce full-size nucleolin, we expressed four N-glycosylation nucleolin variants lacking the N-terminal acidic domain in a baculovirus/insect cell system. As assessed by heptafluorobutyrate derivatization and mass spectrometry, this strategy allowed the production of proteins bearing or not paucimannosidic-type glycans on either one or two of the potential N-glycosylation sites. Their structure was investigated by circular dichroism and fluorimetry, and their ability to self-interact was analyzed by electrophoresis and surface plasmon resonance. Our results demonstrate that all nucleolin-derived variants are able to self-interact and that N-glycosylation on both RBD1 and RBD3, or RBD3 alone, but not RBD1 alone, modifies the structure of the N-terminally truncated nucleolin and enhances its self-association properties. In contrast, N-glycosylation does not modify interaction with lactoferrin, a ligand of cell surface nucleolin. Our results suggest that the occupancy of the N-glycosylation sites may contribute to expression and functions of surface nucleolin.

Binding of Toxoplasma gondii glycosylphosphatidylinositols to galectin-3 is required for their recognition by macrophages.

We showed that the production of tumor necrosis factor (TNF) α by macrophages in response to Toxoplasma gondii glycosylphosphatidylinositols (GPIs) requires the expression of both Toll-like receptors TLR2 and TLR4, but not of their co-receptor CD14. Galectin-3 is a ß-galactoside-binding protein with immune-regulatory effects, which associates with TLR2. We demonstrate here by using the surface plasmon resonance method that the GPIs of T. gondii bind to human galectin-3 with strong affinity and in a dose-dependent manner. The use of a synthetic glycan and of the lipid moiety cleaved from the GPIs shows that both parts are involved in the interaction with galectin-3. GPIs of T. gondii also bind to galectin-1 but with a lower affinity and only through the lipid moiety. At the cellular level, the production of TNF-α induced by T. gondii GPIs in macrophages depends on the expression of galectin-3 but not of galectin-1. This study is the first identification of a galectin-3 ligand of T. gondii origin, and galectin-3 might be a co-receptor presenting the GPIs to the TLRs on macrophages.

A critical review of the roles of host lactoferrin in immunity.

Lactoferrin (Lf) is an essential element of innate immunity, which refers to antigen-nonspecific defense mechanisms that a host uses immediately or within hours after exposure to an antigen. Following infection, Lf is released from neutrophils (PMNs) in blood and inflamed tissues and, such as other soluble pattern-recognition receptors of the innate immunity, Lf recognizes unique microbial molecules called pathogen-associated molecular patterns (PAMPs): LPS from the gram-negative cell wall and bacterial unmethylated CpG DNA. However, unlike classical PAMPs receptors involved in the activation of immune cells, Lf may act either as a competitor for these receptors or as a partner molecule, depending on the physiological status of the organism. These immunomodulatory properties are explained by the ability of Lf to interact with proteoglycans and receptors on the surface of mammalian cells: cells of the innate (NK cells, neutrophils, macrophages, basophils, neutrophils and mast cells) and adaptive [lymphocytes and antigen-presenting cells (APCs)] immune systems, and also epithelial and endothelial cells. Through these interactions, Lf is able to modulate the migration, maturation and functions of immune cells, and thus to influence both adaptive and innate immunities. The understanding of the roles of the host-expressed Lf in immunity comes from in vivo and in vitro studies with exogenous Lf which, although informative, rarely reflect the pathological, or non-pathological, conditions in the organism. In this review, the data from the literature will be critically analyzed in order to present a real picture of the regulatory roles of host Lf in immunity.

Synthesis of heparan sulfate with cyclophilin B-binding properties is determined by cell type-specific expression of sulfotransferases.

Cyclophilin B (CyPB) induces migration and adhesion of T lymphocytes via a mechanism that requires interaction with 3-O-sulfated heparan sulfate (HS). HS biosynthesis is a complex process with many sulfotransferases involved. N-Deacetylases/N-sulfotransferases are responsible for N-sulfation, which is essential for subsequent modification steps, whereas 3-O-sulfotransferases (3-OSTs) catalyze the least abundant modification. These enzymes are represented by several isoforms, which differ in term of distribution pattern, suggesting their involvement in making tissue-specific HS. To elucidate how the specificity of CyPB binding is determined, we explored the relationships between the expression of these sulfotransferases and the generation of HS motifs with CyPB-binding properties. We demonstrated that high N-sulfate density and the presence of 2-O- and 3-O-sulfates determine binding of CyPB, as evidenced by competitive experiments with heparin derivatives, soluble HS, and anti-HS antibodies. We then showed that target cells, i.e. CD4+ lymphocyte subsets, monocytes/macrophages, and related cell lines, specifically expressed high levels of NDST2 and 3-OST3 isoforms. Silencing the expression of NDST1, NDST2, 2-OST, and 3-OST3 by RNA interference efficiently decreased binding and activity of CyPB, thus confirming their involvement in the biosynthesis of binding sequences for CyPB. Moreover, we demonstrated that NDST1 was able to partially sulfate exogenous substrate in the absence of NDST2 but not vice versa, suggesting that both isoenzymes do not have redundant activities but do have rather complementary activities in making N-sulfated sequences with CyPB-binding properties. Altogether, these results suggest a regulatory mechanism in which cell type-specific expression of certain HS sulfotransferases determines the specific binding of CyPB to target cells.

[Lactoferrin: a multifunctional protein]. / La lactoferrine : une protéine multifonctionnelle.

Lactoferrin (Lf) is an iron-binding glycoprotein of the transferrin family that is expressed and secreted by glandular cells and found in the secondary granules of neutrophils from which it is released in infected tissues and blood during the inflammatory process. Initially described as an iron-binding molecule with bacteriostatic properties, Lf is now known to be a multifunctional or multi-tasking protein. It is a major component of the innate immune system of mammals. Its protective effects range from direct anti-microbial activities against a large panel of microorganisms including bacteria, viruses, fungi, and parasites, to anti-inflammatory and anti-cancer activities. While iron chelation is central to some of the biological functions of Lf, other activities involve interactions of Lf with molecular and cellular components of both hosts and pathogens. Its powerful antimicrobial activities, immunomodulatory properties and prevention of septic shock, anti-carcinogenic functions and its growing importance in iron delivery and bone growth, combined with the data obtained either by in vivo studies or clinical trials, make this molecule and its derivatives very promising tools for health or nutritional applications.

The cell surface expressed nucleolin is a glycoprotein that triggers calcium entry into mammalian cells.

Nucleolin is an ubiquitous nucleolar phosphoprotein involved in fundamental aspects of transcription regulation, cell proliferation and growth. It has also been described as a shuttling molecule between nucleus, cytosol and the cell surface. Several studies have demonstrated that surface nucleolin serves as a receptor for various extracellular ligands implicated in cell proliferation, differentiation, adhesion, mitogenesis and angiogenesis. Previously, we reported that nucleolin in the extranuclear cell compartment is a glycoprotein containing N- and O-glycans. In the present study, we show that glycosylation is an essential requirement for surface nucleolin expression, since it is prevented when cells are cultured in the presence of tunicamycin, an inhibitor of N-glycosylation. Accordingly, surface but not nuclear nucleolin is radioactively labeled upon metabolic labeling of cells with [(3)H]glucosamine. Besides its well-demonstrated role in the internalization of specific ligands, here we show that ligand binding to surface nucleolin could also induce Ca(2+) entry into cells. Indeed, by flow cytometry, microscopy and patch-clamp experiments, we show that the HB-19 pseudopeptide, which binds specifically surface nucleolin, triggers rapid and intense membrane Ca(2+) fluxes in various types of cells. The use of several drugs then indicated that Store-Operated Ca(2+) Entry (SOCE)-like channels are involved in the generation of these fluxes. Taken together, our findings suggest that binding of an extracellular ligand to surface nucleolin could be involved in the activation of signaling pathways by promoting Ca(2+) entry into cells.

Proteomic approach to the identification of novel delta-lactoferrin target genes: Characterization of DcpS, an mRNA scavenger decapping enzyme.

The expression of the transcription factor DeltaLf is deregulated in cancer cells. Its overexpression provokes cell cycle arrest along with antiproliferative effects and we recently showed that the Skp1 gene promoter was a target of DeltaLf. Skp1 belongs to the Skp1/Cullin-1/F-box ubiquitin ligase complex responsible for the ubiquitination and the proteosomal degradation of numerous cellular regulators. The transcriptional activity of DeltaLf is highly controlled and negatively regulated by O-GlcNAc, a dynamic post-translational modification known to regulate the functions of many intracellular proteins. We, therefore, constructed a DeltaLf-M4 mutant corresponding to a constitutively active DeltaLf isoform in which all the glycosylation sites were mutated. In order to discover novel targets of DeltaLf transcriptional activity and to investigate the impact of the O-GlcNAc regulation on this activity in situ we compared the proteome profiles of DeltaLf- and DeltaLf-M4-expressing HEK293 cells versus null plasmid transfected cells. A total of 14 differentially expressed proteins were visualized by 2D electrophoresis and silver staining and eight proteins were identified by mass spectrometry analyses (MALDI-TOF; LC-MS/MS), all of which were upregulated. The identified proteins are involved in several processes such as mRNA maturation and stability, cell viability, proteasomal degradation, protein and mRNA quality control. Among these proteins, only DcpS and TCPB were also upregulated at the mRNA level. Analysis of their respective promoters led to the detection of a cis-regulating element in the DcpS promoter. The S1(DcpS) is 80% identical to the S1 sequence previously described by He and Furmanski [Sequence specificity and transcriptional activation in the binding of lactoferrin to DNA, Nature 373 (1995) 721-724]. Reporter gene analyses and ChIP assays demonstrated that DeltaLf interacts specifically with the DcpS promoter in vivo. These data established that DcpS, a key enzyme in mRNA decay, is a new target of DeltaLf transcriptional activity.

Nanoscale devices for online dielectric spectroscopy of biological cells.

Nanoscale probes have been developed for the online characterization of the electrical properties of biological cells by dielectric spectroscopy. Two types of sensors have been designed and fabricated. The first one is devoted to low (<10 MHz) frequency range analysis and consists of gold nanoelectrodes. The second one works for high (>40 Hz) frequency range analysis and consists of a gold nanowire. The patterning of the sensors is performed by electron beam lithography. These devices are integrated in a microfluidic channel network for the manipulation of the cells and for the improvement of the performances of the sensors. These devices are used for the analysis of a well-characterized biological model in the area of the ligand-receptor interaction. The purpose is to monitor the interaction between the lactoferrin (the ligand) and the nucleolin and sulfated proteoglycans (the receptors) present or not on a set of mutant Chinese hamster ovary cell lines and their following internalization into the cytoplasm. Initial measurements have been performed with this microsystem and they demonstrate its capability for label-free, real-time, analysis of a dynamic mechanism involving biological cells.

Lactoferrin structure and functions.

Lactoferrin (Lf) is an iron binding glycoprotein of the transferrin family that is expressed in most biological fluids and is a major component of mammals' innate immune system. Its protective effect ranges from direct antimicrobial activities against a large panel of microorganisms, including bacteria, viruses, fungi, and parasites, to anti-inflammatory and anticancer activities. This plethora of activities is made possible by mechanisms of action implementing not only the capacity of Lf to bind iron but also interactions of Lf with molecular and cellular components of both host and pathogens. This chapter summarizes our current understanding of the Lf structure-function relationships that explain the roles of Lf in host defense.

Mycobacterial lipomannan induces MAP kinase phosphatase-1 expression in macrophages.

Mycobacterial lipomannan (LM) and lipoarabinomannan (LAM) regulate macrophage activation by interacting with Toll-like receptors (TLRs). The intracellular signalling pathways elicited by these complex molecules are poorly defined. We have demonstrated that LM purified from various mycobacterial species, but not LAM from Mycobacterium kansasii or Mycobacterium bovis BCG, induced expression of the MAP kinase phosphatase 1 (MKP-1) in macrophages. Anti-TLR2 antibodies, as well as specific ERK and p38 MAPK inhibitors, decreased MKP-1 transcription in LM-stimulated cells. These findings suggest that the binding of LM to TLR2 triggers MAPK activation, followed by an up-regulation of MKP-1 expression, which in turn may act as a negative regulator of MAPK activation.

Cyclophilin B induces integrin-mediated cell adhesion by a mechanism involving CD98-dependent activation of protein kinase C-delta and p44/42 mitogen-activated protein kinases.

Initially identified as a cyclosporin-A binding protein, cyclophilin B (CyPB) is an inflammatory mediator that induces adhesion of T lymphocytes to fibronectin, by a mechanism dependent on CD147 and alpha 4 beta 1 integrins. Recent findings have suggested that another cell membrane protein, CD98, may cooperate with CD147 to regulate beta1 integrin functions. Based on these functional relationships, we examined the contribution of CD98 in the pro-adhesive activity of CyPB, by utilizing the responsive promonocyte cell line THP-1. We demonstrated that cross-linking CD98 with CD98-AHN-18 antibody mimicked the responses induced by CyPB, i.e. homotypic aggregation, integrin-mediated adhesion to fibronectin and activation of p44/42 MAPK. Consistent with previous data, immunoprecipitation confirmed the existence of a heterocomplex wherein CD147, CD98 and beta1 integrins were associated. We then demonstrated that CyPB-induced cell adhesion and p44/42 MAPK activation were dependent on the participation of phosphoinositide 3-kinase and subsequent activation of protein kinase C-delta. Finally, silencing the expression of CD98 by RNA interference potently reduced CyPB-induced cell responses, thus confirming the role of CD98 in the pro-adhesive activity of CyPB. Altogether, our results support a model whereby CyPB induces integrin-mediated adhesion via interaction with a multimolecular unit formed by the association between CD147, CD98 and beta1 integrins.

The heparin/heparan sulfate sequence that interacts with cyclophilin B contains a 3-O-sulfated N-unsubstituted glucosamine residue.

Many of the biological functions of heparan sulfate (HS) proteoglycans can be attributed to specialized structures within HS moieties, which are thought to modulate binding and function of various effector proteins. Cyclophilin B (CyPB), which was initially identified as a cyclosporin A-binding protein, triggers migration and integrin-mediated adhesion of peripheral blood T lymphocytes by a mechanism dependent on interaction with cell surface HS. Here we determined the structural features of HS that are responsible for the specific binding of CyPB. In addition to the involvement of 2-O,6-O, and N-sulfate groups, we also demonstrated that binding of CyPB was dependent on the presence of N-unsubstituted glucosamine residues (GlcNH2), which have been reported to be precursors for sulfation by 3-O-sulfotransferases-3 (3-OST-3). Interestingly, 3-OST-3B isoform was found to be the main 3-OST isoenzyme expressed in peripheral blood T lymphocytes and Jurkat T cells. Moreover, down-regulation of the expression of 3-OST-3 by RNA interference potently reduced CyPB binding and consequent activation of p44/42 mitogen-activated protein kinases. Altogether, our results strongly support the hypothesis that 3-O-sulfation of GlcNH2 residues could be a key modification that provides specialized HS structures for CyPB binding to responsive cells. Given that 3-O-sulfation of GlcNH2-containing HS by 3-OST-3 also provides binding sites for glycoprotein gD of herpes simplex virus type I, these findings suggest an intriguing structural linkage between the HS sequences involved in CyPB binding and viral infection.

Identification by surface plasmon resonance of the mycobacterial lipomannan and lipoarabinomannan domains involved in binding to CD14 and LPS-binding protein.

The mycobacterial lipoglycans, lipomannan (LM) and lipoarabinomannan (LAM), regulate host defence mechanisms through their interaction with pattern recognition receptors such as Toll-like receptors (TLRs). We have developed a surface plasmon resonance assay to analyse the molecular basis for the recognition of Mycobacterium kansasii LM or LAM, by immobilized CD14 and LPS-binding protein (LBP) both being capable to promote presentation of bacterial glycolipids to TLRs. The affinity of either LM/LAM was higher to CD14 than to LBP. Kinetic and Scatchard analyses were consistent with a model involving a single class of binding sites. These interactions required the lipidic anchor, but not the carbohydrate domains, of LM or LAM. We also provide evidence that addition of recombinant LBP enhanced the stimulatory effect of LM or LAM on matrix metalloproteinase-9 expression and secretion in macrophages, through a TLR1/TLR2-dependent mechanism.

Human delta-lactoferrin is a transcription factor that enhances Skp1 (S-phase kinase-associated protein) gene expression.

Delta-lactoferrin is a cytoplasmic lactoferrin isoform that can locate to the nucleus, provoking antiproliferative effects and cell cycle arrest in S phase. Using macroarrays, the expression of genes involved in the G(1)/S transition was examined. Among these, Skp1 showed 2-3-fold increased expression at both the mRNA and protein levels. Skp1 (S-phase kinase-associated protein) belongs to the Skp1/Cullin-1/F-box ubiquitin ligase complex responsible for the ubiquitination of cellular regulators leading to their proteolysis. Skp1 overexpression was also found after delta-lactoferrin transient transfection in other cell lines (HeLa, MDA-MB-231, HEK 293) at comparable levels. Analysis of the Skp1 promoter detected two sequences that were 90% identical to those previously known to interact with lactoferrin, the secretory isoform of delta-lactoferrin (GGCACTGTAC-S1(Skp1), located at - 1067 bp, and TAGAAGTCAA-S2(Skp1), at - 646 bp). Both gel shift and chromatin immunoprecipitation assays demonstrated that delta-lactoferrin interacts in vitro and in vivo specifically with these sequences. Reporter gene analysis confirmed that delta-lactoferrin recognizes both sequences within the Skp1 promoter, with a higher activity on S1(Skp1). Deletion of both sequences totally abolished delta-lactoferrin transcriptional activity, identifying them as delta-lactoferrin-responsive elements. Delta-lactoferrin enters the nucleus via a short bipartite RRSDTSLTWNSVKGKK(417-432) nuclear localization signal sequence, which was demonstrated to be functional using mutants. Our results show that delta-lactoferrin binds to the Skp1 promoter at two different sites, and that these interactions lead to its transcriptional activation. By increasing Skp1 gene expression, delta-lactoferrin may regulate cell cycle progression via control of the proteasomal degradation of S-phase actors.

Syndecan-1/CD147 association is essential for cyclophilin B-induced activation of p44/42 mitogen-activated protein kinases and promotion of cell adhesion and chemotaxis.

Many of the biological functions attributed to cell surface proteoglycans are dependent on the interaction with extracellular mediators through their heparan sulphate (HS) moieties and the participation of their core proteins in signaling events. A class of recently identified inflammatory mediators is secreted cyclophilins, which are mostly known as cyclosporin A-binding proteins. We previously demonstrated that cyclophilin B (CyPB) triggers chemotaxis and integrin-mediated adhesion of T lymphocytes mainly of the CD4+/CD45RO+ phenotype. These activities are related to interactions with two types of binding sites, CD147 and cell surface HS. Here, we demonstrate that CyPB-mediated adhesion of CD4+/CD45RO+ T cells is related to p44/42 mitogen-activated protein kinase (MAPK) activation by a mechanism involving CD147 and HS proteoglycans (HSPG). Although HSPG core proteins are represented by syndecan-1, -2, -4, CD44v3 and betaglycan in CD4+/CD45RO+ T cells, we found that only syndecan-1 is physically associated with CD147. The intensity of the heterocomplex increased in response to CyPB, suggesting a transient enhancement and/or stabilization in the association of CD147 to syndecan-1. Pretreatment with anti-syndecan-1 antibodies or knockdown of syndecan-1 expression by RNA interference dramatically reduced CyPB-induced p44/p42 MAPK activation and consequent migration and adhesion, supporting the model in which syndecan-1 serves as a binding subunit to form the fully active receptor of CyPB. Altogether, our findings provide a novel example of a soluble mediator in which a member of the syndecan family plays a critical role in efficient interaction with signaling receptors and initiation of cellular responses.

Interactions of lactoferrin with cells involved in immune function.

The antimicrobial activities of lactoferrin (Lf) depend on its capacity to bind iron and on its direct interaction with the surface of microorganisms. Its protective effect also extends to the regulation of the host response to infections. Depending on the immune status of an individual, Lf can have anti-inflammatory properties that downregulate the immune response and prevent septic shock and damage to tissues. It also acts as a promoter of the activation, differentiation, and (or) proliferation of immune cells. Although most of the anti-inflammatory activities are correlated with the neutralization of proinflammatory molecules by Lf, the promoting activity seems to be related to a direct effect of Lf on immune cells. Although the mechanisms that govern these activities are not clearly defined, and probably differ from cell to cell, several cellular targets and possible mechanisms of action are highlighted. The majority of the molecular targets at the surface of cells are multiligand receptors but, interestingly, most of them have been reported as signaling, endocytosis, and nuclear-targeting molecules. This review focuses on the known and putative mechanisms that allow the immunoregulating effect of Lf in its interactions with immune cells.

Mycobacterial lipomannan induces matrix metalloproteinase-9 expression in human macrophagic cells through a Toll-like receptor 1 (TLR1)/TLR2- and CD14-dependent mechanism.

Lipomannans (LM) from various mycobacterial species were found to induce expression and secretion of the matrix metalloproteinase 9 (MMP-9) both in human macrophage-like differentiated THP-1 cells and in primary human macrophages. Inhibition studies using antireceptor-neutralizing antibodies are indicative of a Toll-like receptor 1 (TLR1)/TLR2- and CD14-dependent signaling mechanism. Moreover, LM was shown to down-regulate transcription of the metalloproteinase inhibitor TIMP-1, a major endogenous MMP-9 regulator.

Nucleolin undergoes partial N- and O-glycosylations in the extranuclear cell compartment.

Nucleolin is an ubiquitous, nonhistone nucleolar phosphoprotein involved in fundamental aspects of transcription regulation, cell proliferation, and growth. Nucleolin was primarily found in the nucleus, but it was also proposed as a possible shuttle between the nucleus, cytoplasm, and cell membrane. We report here that part of the extranuclear nucleolin undergoes complex N- and O-glycosylations. A band with higher molecular mass (113 kDa) than the 105-kDa classical major nucleolin band was detected on SDS-PAGE gel that cross-reacted with specific anti-nucleolin antibodies and was identified as a nucleolin isoform by mass spectrometry. The presence of N-glycans was first suggested by sensibility of the 113-kDa nucleolin isoform to tunicamycin treatment. Determination of monosaccharide composition by heptafluorobutyrate derivation followed by gas-chromatography mass spectrometry indicated the presence of N- and O-glycans. The structures of N- and O-glycans were first investigated using specificity of binding to lectins. This approach allowed a partial characterization of N-glycan structures and revealed O-glycan structures that could otherwise go unnoticed. Further study of N-glycans by mass spectrometry using direct exoglycosidase treatment on MALDI-TOF target allowed the complete definition of their structures. Finally, the use of peptide mass fingerprinting with sinapinic acid allowed identification of N317 and N492 as the two N-glycosylation sites. N317 and N492 belong to RNA-binding domains 1 and 3 of nucleolin, respectively, that suggests a role of glycosylation in regulating the function of the protein.

Expression and prognostic value of lactoferrin mRNA isoforms in human breast cancer.

We investigated the expression levels of human lactoferrin (Lf), a steroid hormone-inducible gene product the expression of which is often altered during oncogenesis, and of Delta-lactoferrin (DeltaLf), its alternative isoform, which has been shown to be absent from tumor cell lines in commonly used human breast epithelial cell lines, using semiquantitative RT-PCR. Both mRNAs were detected but with levels of expression lower than those found in normal breast epithelial cells. This downregulation was much more visible for DeltaLf since its expression was either significantly diminished (BT-20, MCF-7 cell lines) or practically absent (MDA-MB-231, T-47D, HBL 100 cell lines). In order to determine whether Lf gene products are useful prognosic tools, we further analyzed their expression levels in 99 primary breast cancer biopsies. DeltaLf transcripts were found in all of the samples, whereas Lf transcripts were found in 88% of them. Lf and DeltaLf expression levels were positively correlated (p = 0.003). Lf expression was related to tumor type with a higher recovery in lobular-type tumors (p = 0.04). DeltaLf expression was related to the histoprognostic grading (p = 0.02). In univariate analyses, DeltaLf and Lf expressions were prognosis parameters, high concentrations being associated with a longer overall survival.

Lactoferrin and host defence: an overview of its immuno-modulating and anti-inflammatory properties.

Lactoferrin is a member of the transferrin family of iron-binding glycoproteins that is abundantly expressed and secreted from glandular epithelial cells. In secretions, such as milk and fluids of the intestinal tract, lactoferrin is an important component of the first line of host defence. During the inflammatory process, lactoferrin, a prominent component of the secondary granules of neutrophils (PMNs), is released in infected tissues and in blood and then it is rapidly cleared by the liver. In addition to the antimicrobial properties of lactoferrin, a set of studies has focused on its ability to modulate the inflammatory process and the overall immune response. Though many in vitro and in vivo studies report clear regulation of the immune response and protective effect against infection and septic shock by lactoferrin, elucidation of all the cellular and molecular mechanisms of action is far from being achieved. At the cellular level, lactoferrin modulates the migration, maturation and function of immune cells. At the molecular level and in addition to iron binding, interactions of lactoferrin with a plethora of compounds, either soluble or membrane molecules, account for its modulatory properties. This paper reviews our current understanding of the cellular and molecular mechanisms that explain the regulatory properties of lactoferrin in host defence.