Lactoferrin and host defense

Human ceruminous gland: Ultrastructure and histochemical analysis of antimicrobial and cytoskeletal components

The ceruminous glands in the skin of the human external auditory canal are modified apocrine glands, which, together with sebaceous glands, produce the cerumen, the ear wax. Cerumen plays an important role in the protection of the ear canal against physical damage and microbial invasion. We studied the morphology of the glandular cells by light and electronmicroscopy. Antimicrobial and cytoskeletal components of the ceruminous glands were investigated by immunohistochemical methods. Numerous antimicrobial proteins and peptides are present in the ceruminous glandular cells: beta-defensin-1, beta-defensin-2, cathelicidin, lysozyme, lactoferrin, MUC1, secretory component of IgA. These data indicate a crucial role in the innate host defense against diverse pathogens. The apocrine secretion mechanism is a special mode of secretion by which the apical part of the cell cytoplasm surrounded by a membrane is pinched off. We could show that the presence of actin filaments, CK 19 and CK 7, seems to play a role in the pinching-off mechanism. Finally, we showed the secretion of lipid vesicles from the ceruminous gland. We could extend the number of detected antimicrobial peptides and proteins in human ceruminous glandular cells that protect the surface of the external auditory meatus. In addition, we detected proteins involved in the apocrine secretion mode of the ceruminous gland.

Gene expression alterations in the non-neoplastic parenchyma adjacent to infiltrating pancreatic ductal adenocarcinoma

The non-neoplastic pancreatic parenchyma adjacent to infiltrating ductal adenocarcinoma demonstrates inflammation, fibrosis, acinar cell loss and small duct-like metaplasia of acinar cells. Similar morphologic changes are also observed in the setting of chronic pancreatitis. In addition, peritumoral acini have been shown to have alterations in gene expression even in the absence of morphological changes. To better understand the pancreatic acinar responses to infiltrating pancreatic ductal adenocarcinoma, we characterized gene expression patterns of pancreatic acinar tissue adjacent to infiltrating pancreatic ductal adenocarcinomas and compared them to gene expression patterns of acinar tissue affected by chronic pancreatitis as well as to those of normal pancreatic acini. Fresh-frozen pancreatic acinar tissue was microdissected from nine patients (three with pancreatic cancer, three with chronic pancreatitis, three with normal pancreata) using laser capture microdissection, and extracted RNA from each microdissection was subjected to two rounds of linear amplification and hybridized to oligonucleotide microarrays. Gene expression patterns were confirmed using quantitative RT-PCR and/or immunohistochemistry. A total of 20 genes was found to be overexpressed in peritumoral acinar tissue compared to normal acinar tissue and to acini affected by chronic pancreatitis. These 20 genes included pancreatitis-associated protein (HIP/PAP), a gene known to be overexpressed in acini adjacent to infiltrating pancreatic cancer, and the gene cartilage glycoprotein-39 (HC gp-39 or TKL-40). Serum HC gp-39 protein levels were significantly higher in patients with pancreatic cancer and in those with chronic pancreatitis than in controls without pancreatic disease. There was no significant difference in the levels of serum HC gp-39 in patients with pancreatic cancer and those with chronic pancreatitis. Our results demonstrate some of the molecular alterations in acinar cells that occur in response to adjacent infiltrating pancreatic ductal adenocarcinoma and reveal that such alterations can provide a rich source of markers of pancreatic cancer.

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.

Suppressive effects of milk-derived lactoferrin on psychological stress in adult rats

Lactoferrin (LF) is known as an iron-binding glycoprotein. It has been shown that bovine LF (bLF) is transported into cerebrospinal fluid via blood although its physiological effects in the central nervous system (CNS) are still unclear. In this study, a suppressive effect of bLF on psychological distress was investigated in adult rats. Intraperitoneal injection of bLF (100 mg/kg) reduced stressful behaviors in a conditioned fear-induced freezing test and an elevated plus-maze test. Interestingly, the suppressive effect of bLF was enhanced by pretreatment with electric foot-shock (FS). This suppressive effect of bLF in the elevated plus-maze test was reversed by pretreatment with naloxone, an opioid receptor antagonist, at a dose of 1 mg/kg (ip). N(omega)-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase (NOS) inhibitor, also blocked the suppressive effect of bLF and foot-shock. In addition, combined application of a low dose of bLF (30 mg/kg, ip) and l-arginine (30 and 100 mg/kg, ip) showed significant potentiated effects on psychological stress. These results suggest that bLF has suppressive effects on psychological distress, especially under the condition of moderate stress. Furthermore, it is suggested that bLF possibly activates an endogenous opioidergic system via nitric oxide synthase activation.

Iron and microbial infection

The use of iron as a cofactor in basic metabolic pathways is essential to both pathogenic microorganisms and their hosts. It is also a pivotal component of the innate immune response through its role in the generation of toxic oxygen and nitrogen intermediates. During evolution, the shared requirement of micro- and macroorganisms for this important nutrient has shaped the pathogen-host relationship. Here, we discuss how pathogens compete with the host for iron, and also how the host uses iron to counteract this threat.

cDNA microarray analysis of lactoferrin expression in non-neoplastic human hepatocyte PH5CH8 cells

Lactoferrin (LF), a milk protein belonging to the iron transporter transferrin family, is known as a primary defense protein against pathogenic microorganisms. Previously, we found that bovine and human LFs prevented hepatitis C virus infection in cultured human hepatocytes by a direct interaction with the virus. Since LF is proposed to have transcriptional regulatory activity in addition to its antimicrobial function, we sought to identify the target genes that these two types of LF have in common. To this end, we were the first to perform microarray analysis (9970 genes) using human hepatocytes that expressed bovine or human LF by retrovirus-mediated gene transfer. In the results, LF could give a variety of expression profiles in the human hepatocytes, and showed that 9 and 19 genes were commonly up-regulated (more than 2.0-fold) and down-regulated (less than 0.50-fold), respectively, in both bovine and human LF-expressing cells compared with control cells. Among these genes, we found that gamma-aminobutyric acid (GABA)-B receptor 2 was transcriptionally down-regulated by bovine and human LFs, but not by human transferrin. Furthermore, we obtained the suggestive result that LF may modulate the level of intracellular cAMP. This modulation is one of the cellular responses that the GABA-B receptor modifies. This is the first report of microarray analysis applied to search inclusively for the target genes of LF.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Human Apo-Lactoferrin Enhances Angiogenesis Mediated by Vascular Endothelial Growth Factor A in vivo

BACKGROUND

Lactoferrin, LF, a multifunctional iron- and heparin-binding protein, present in exocrine body secretions and leukocytes, is remarkably resistant to proteolysis. Ingested bovine iron-unsaturated LF, apo-bLF, suppresses VEGF-A-mediated angiogenesis in a previously described rat mesentery angiogenesis assay, possibly explaining, at least in part, its established anticancer effect in rats and mice.

METHODS

Using the same experimental system, we have now studied the effect of (i) ingested human apo-LF, apo-hLF, on angiogenesis mediated by VEGF-A and bFGF, (ii) ingested human iron-saturated LF, holo-hLF, on VEGF-A-mediated angiogenesis and (iii) subcutaneous continuously infused apo-hLF on VEGF-A-mediated angiogenesis.

RESULTS

Ingested holo-hLF did not affect VEGF-A-mediated angiogenesis. Ingested apo-hLF (from one and the same batch) significantly enhanced VEGF-A-mediated angiogenesis but did not affect bFGF-mediated angiogenesis. Moreover, subcutaneously infused apo-hLF also significantly stimulated VEGF-A-mediated angiogenesis.

CONCLUSION

Taken together, the data suggest that apo-hLF exerts a specific proangiogenic effect in VEGF-A-mediated angiogenesis. Clearly, human and bovine apo-LF exert opposite effects on VEGF-A-induced angiogenesis. Differences in molecular features between human and bovine LFs of possible significance for the outcome are discussed. In hypoxia, compensatory collateral circulation is mediated primarily by VEGF-A. We hypothesize that systemically administered apo-hLF may promote collateral blood vessel formation at hypoxic sites in normal tissue, thus counteracting ischemia and infarction.

The Low-Density Lipoprotein Receptor-Related Protein 1 Is a Mitogenic Receptor for Lactoferrin in Osteoblastic Cells

Lactoferrin induces osteoblast proliferation and survival in vitro and is anabolic to bone in vivo. The molecular mechanisms by which lactoferrin exerts these biological actions are not known, but lactoferrin is known to bind to two members of the low-density lipoprotein receptor family, low- density lipoprotein receptor-related proteins 1 (LRP1) and 2 (LRP2). We have examined the role(s) of these receptors in the actions of lactoferrin on osteoblasts. We show that lactoferrin binds to cultured osteoblastic cells, and that LRP1 and LRP2 are expressed in several osteoblastic cell types. In primary rat osteoblastic cells, the LRP1/2 inhibitor receptor associated protein blocks endocytosis of lactoferrin and abrogates lactoferrin-induced p42/44 MAPK signaling and mitogenesis. Lactoferrin-induced mitogenesis is also inhibited by an antibody to LRP1. Lactoferrin also induces receptor associated protein-sensitive activation of p42/44 MAPK signaling and proliferation in osteoblastic human SaOS-2 cells, which express LRP1 but not LRP2. The mitogenic response of LRP1-null fibroblastic cells to lactoferrin is substantially reduced compared with that of cells expressing wild-type LRP1. The endocytic and signaling functions of LRP1 are independent of each other, because lactoferrin can activate mitogenic signaling in conditions in which endocytosis is inhibited. Taken together, these results 1) suggest that mitogenic signaling through LRP1 to p42/44 MAPKs contributes to the anabolic skeletal actions of lactoferrin; 2) demonstrate growth-promoting actions of a third LRP family member in osteoblasts; and 3) provide further evidence that LRP1 functions as a signaling receptor in addition to its recognized role in ligand endocytosis.

PspA protects Streptococcus pneumoniae from killing by apolactoferrin, and antibody to PspA enhances killing of pneumococci by apolactoferrin [corrected]

Lactoferrin is an important component of innate immunity through its sequestration of iron, bactericidal activity, and immune modulatory activity. Apolactoferrin (ALF) is the iron-depleted form of lactoferrin and is bactericidal against pneumococci and several other species of bacteria. We observed that lactoferricin (LFN), an 11-amino-acid peptide from the N terminus of lactoferrin, is bactericidal for Streptococcus pneumoniae. Strains of S. pneumoniae varied in their susceptibility to ALF. Lactoferrin is bound to the pneumococcal surface by pneumococcal surface protein A (PspA). Using mutant PspA(-) pneumococci of four different strains, we observed that PspA offers significant protection against killing by ALF. Knockout mutations in genes for two other choline-binding proteins (PspC and PcpA) did not affect killing by ALF. PspA did not have to be attached to the bacterial surface to inhibit killing, because the soluble recombinant N-terminal half of PspA could prevent killing by both ALF and LFN. An 11-amino-acid fragment of PspA was also able to reduce the killing by LFN. Antibody to PspA enhanced killing by lactoferrin. These findings suggested that the binding of ALF to PspA probably blocks the active site(s) of ALF that is responsible for killing.

Oral administration of bovine whey proteins to mice elicits opposing immunoregulatory responses and is adjuvant dependent

Most studies investigating the induction of oral tolerance (OT) use purified proteins such as ovalbumin (OVA), bovine serum albumin (BSA) and beta-lactoglobulin (beta-LG). Little information is available regarding the induction of OT to a protein mixture, e.g. cow's milk. In this study we compared the regulatory mechanisms induced after the oral administration of a whey protein concentrate (WP) derived from cow's milk following immunization with two different adjuvants, complete Freund's adjuvant (CFA) and alum. OVA was used as a control antigen. Animals were given a single feed of these proteins at an equivalent dose of 1 mg/g body weight before they were immunized seven days later with the antigen in Freund's adjuvant or alum. Delayed type hypersensitivity (DTH) responses were suppressed by both a feed of WP and OVA after immunization with CFA. However, only OVA feeding suppressed antigen specific IgG responses. In an attempt to investigate whether WP would tolerize the more susceptible IgE responses, alum immunization replaced CFA as the adjuvant used for systemic immunizations. WP, after a single feed, significantly primed for DTH and IgE responses indicating oral sensitization to WP. In contrast, OVA suppressed DTH, IgE and IgG responses. Antigen specific proliferation of mononuclear cells was suppressed in mice fed OVA, but primed in those fed with WP. In addition cells taken from sensitized mice fed WP up-regulated levels of specific interleukin (IL) -4, -10 and -12 in vitro whereas these cytokines were suppressed in cultures from tolerant WP fed mice. Global suppression was obtained in cultures from tolerant OVA fed mice. TGF-beta was not detected in draining PLN cell cultures of either tolerant or sensitized mice. These data suggest that a whey protein mixture induces divergent responses following immunization with either CFA or alum despite being fed at an identical dose. We suggest that that the choice of the adjuvant may determine the immunoregulatory outcome and this is also reflected by the systemic cytokine profile.

Nomenclature of the Proteins of Cows’ Milk—Sixth Revision

This report of the American Dairy Science Association Committee on the Nomenclature, Classification, and Methodology of Milk Proteins reviews changes in the nomenclature of milk proteins necessitated by recent advances of our knowledge of milk proteins. Identification of major caseins and whey proteins continues to be based upon their primary structures. Nomenclature of the immunoglobulins consistent with new international standards has been developed, and all bovine immunoglobulins have been characterized at the molecular level. Other significant findings related to nomenclature and protein methodology are elucidation of several new genetic variants of the major milk proteins, establishment by sequencing techniques and sequence alignment of the bovine caseins and whey proteins as the reference point for the nomenclature of all homologous milk proteins, completion of crystallographic studies for major whey proteins, and advances in the study of lactoferrin, allowing it to be added to the list of fully characterized milk proteins.

Apocrine Glands in the Eyelid of Primates Contribute to the Ocular Host Defense

Apocrine glands of Moll are regular components of primate eyelids. We studied the distribution and localization of these glands in three different primate species, the common marmoset, the rhesus monkey, and the hamadryas baboon. In addition, we tested the primate glands of Moll with antibodies against antimicrobial proteins, cytoskeletal proteins and the androgen receptor. The glands of Moll differ in abundance and distribution in different monkeys. In the common marmoset, a representative of the New World monkeys, Platyrrhini, the apocrine glands are frequently found at the lid margin and in the overlying epidermis of the lid. In the rhesus monkey and the hamadryas baboon, representatives of Old World monkeys, Catarrhini, apocrine glands are rarer and located predominantly at the margin of the lid. The immunohistochemical analysis indicates the presence of a variety of antimicrobial proteins, e.g. lysozyme, beta-defensin-2, adrenomedullin, lactoferrin, and IgA, in these glands. Interestingly, there are basically no androgen receptors in the nuclei of apocrine glands at the lid margin in all three monkey species. In the common marmoset, however, androgen receptors are found in apocrine glands of the overlying epidermis of the lid. We speculate that the glands of Moll are derived from apocrine glands as found in the skin of the entire body in New World monkeys which developed at the lid margins of higher primates and humans into specialized glands secreting agents of host defense in the eye.

Effects of bovine lactoferrin hydrolysate on the in vitro antimicrobial susceptibility of Escherichia coli strains isolated from baby pigs

OBJECTIVE

To determine the antibacterial activity of bovine lactoferrin hydrolysate (bLf-lysate) alone or in combination with other antimicrobials against antimicrobial-resistant Escherichia coli strains isolated from baby pigs.

SAMPLE POPULATION

3 clinical strains of E coli were isolated from baby pigs with severe diarrhea and designated as strains 9061, 9062, and 9065.

PROCEDURE

The broth microdilution checkerboard and fractional inhibitory (or bactericidal) concentration index were used to evaluate the antibacterial effect elicited by bLf-lysate in combination with kanamycin, gentamicin, cephalothin, cefamandole, penicillin G, ampicillin, tetracycline, erythromycin, or rifampicin against the 3 strains of E coli.

RESULTS

The 3 strains of E coli were susceptible to gentamicin and rifampicin but highly resistant to most of the other antimicrobials tested, except for strain 9061 that was also susceptible to cephalothin but intermediately inhibited by kanamycin and cefamandole. Synergistic growth-inhibitory activity was observed between bLf-lysate and gentamicin against 1 strain of E coli (strain 9062); synergistic bactericidal activity was found between bLf-lysate and rifampicin against all 3 strains of E coli. Moreover, partial synergy was observed between bLf-lysate and kanamycin, gentamicin, cephalothin, or cefamandole against the strains of E coli, but this partial synergistic activity was mostly seen against only 1 of the strains. Little interaction between bLf-lysate and tetracycline, ampicillin, penicillin G, or erythromycin was observed against the clinical strains of E coli.

CONCLUSIONS AND CLINICAL RELEVANCE

A combination of bLf-lysate and certain antimicrobials may prove clinically effective against antimicrobial-resistant strains of E coli.

Surface nucleolin participates in both the binding and endocytosis of lactoferrin in target cells

Lactoferrin (Lf), a multifunctional molecule present in mammalian secretions and blood, plays important roles in host defense and cancer. Indeed, Lf has been reported to inhibit the proliferation of cancerous mammary gland epithelial cells and manifest a potent antiviral activity against human immunodeficiency virus and human cytomegalovirus. The Lf-binding sites on the cell surface appear to be proteoglycans and other as yet undefined protein(s). Here, we isolated a Lf-binding 105 kDa molecular mass protein from cell extracts and identified it as human nucleolin. Medium-affinity interactions ( approximately 240 nm) between Lf and purified nucleolin were further illustrated by surface plasmon resonance assays. The interaction of Lf with the cell surface-expressed nucleolin was then demonstrated through competitive binding studies between Lf and the anti-human immunodeficiency virus pseudopeptide, HB-19, which binds specifically surface-expressed nucleolin independently of proteoglycans. Interestingly, binding competition studies between HB-19 and various Lf derivatives in proteoglycan-deficient hamster cells suggested that the nucleolin-binding site is located in both the N- and C-terminal lobes of Lf, whereas the basic N-terminal region is dispensable. On intact cells, Lf co-localizes with surface nucleolin and together they become internalized through vesicles of the recycling/degradation pathway by an active process. Morever, a small proportion of Lf appears to translocate in the nucleus of cells. Finally, the observations that endocytosis of Lf is inhibited by the HB-19 pseudopeptide, and the lack of Lf endocytosis in proteoglycan-deficient cells despite Lf binding, point out that both nucleolin and proteoglycans are implicated in the mechanism of Lf endocytosis.

Lactoferrin impairs type III secretory system function in enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) is an important cause of infant diarrhea in developing countries. EPEC uses a type III secretory system to deliver effector proteins into the host cell. These proteins cause the characteristic attaching and effacing lesion on enterocytes. Lactoferrin, a glycoprotein present in human milk, inhibits EPEC adherence to mammalian cells. To determine the effect of lactoferrin on the initial host cell attachment step that is mediated by the type III secretory system, we focused on EPEC-induced actin polymerization in HEp2 cells, on the hemolytic activity, and on measurement of E. coli secreted proteins A, B, and D (EspABD). Lactoferrin blocked EPEC-mediated actin polymerization in HEp2 cells and blocked EPEC-induced hemolysis. The mechanism of this inhibition was lactoferrin-mediated degradation of secreted proteins necessary for bacterial contact and pore formation, particularly EspB. The proteolytic effect of lactoferrin was prevented by serine protease inhibitors. This disruption of the type III secretory system implies that lactoferrin could provide broad cross protection against the enteropathogens that share this mechanism.

Ozone-induced disruptions of lung transcriptomes

We have analyzed changes in approximately 4000 lung mRNAs, with GeneChips, in mice exposed to 1 ppm O(3) for three consecutive nights (8 h per night). Differential gene expression analysis identified approximately 260 O(3) sensitive genes; approximately 80% of these were repressed and approximately 20% were induced in O(3)-exposed mice compared to the air-exposed controls. A 20-fold induction of serum amyloid A3 mRNA by O(3) suggested activation of NF-kappaB and CCAAT/enhancer binding protein-mediated pathways by inflammatory cytokines. Induction (up to 14-fold) of 12 genes that increase DNA synthesis and cell cycle progression, and increase (approximately 7-fold) in CD44 mRNA and macrophage metalloelastase suggested a state of O(3)-induced hyperplasia and lung remodeling. Several mRNAs encoding enzymes of xenobiotic metabolism and cytoskeletal functions were repressed and may suggest cytokine mediated suppression of cytochrome P450 expression and cachexia-like inflammatory state in ozone-exposed lungs. The expressions of approximately 30 genes of immune response were also repressed. Collectively this genome-wide analysis of lungs identified ozone-induced disruption of gene transcriptional profile indicative of increased cellular proliferation under suppressed immune surveillance and xenobiotic metabolism.

An intronic alternative promoter of the human lactoferrin gene is activated by Ets

Lactoferrin expresses in a variety of tissues and involves in various aspects of host defense mechanisms. The lactoferrin gene is differentially regulated through multiple signaling pathways. Recently, an alternative form of human lactoferrin mRNA (Delta LF) was found in normal human tissues but absent from the tumor cells. In this study, we identified the transcription start sites of the Delta LF in mammary gland and bone marrow and demonstrated that the Delta LF is the product of an alternative (P2) promoter present in the first intron of the lactoferrin gene. The P2 promoter has high activity in Jurkat and U937 and low activity in RL95-2 and HEC-1B cell lines. Nonetheless, the promoter activity in HEC-1B cells was dramatically enhanced with overexpression of the Ets-1 transcription factor. The GFP-tagged lactoferrin is present in the cytoplasm whereas GFP-tagged Delta LF is found in both nucleus and cytoplasm as examined by fluorescence and confocal microscopy.

Iron status in mice carrying a targeted disruption of lactoferrin

Lactoferrin is a member of the transferrin family of iron-binding glycoproteins present in milk, mucosal secretions, and the secondary granules of neutrophils. While several physiological functions have been proposed for lactoferrin, including the regulation of intestinal iron uptake, the exact function of this protein in vivo remains to be established. To directly assess the physiological functions of lactoferrin, we have generated lactoferrin knockout (LFKO(-/-)) mice by homologous gene targeting. LFKO(-/-) mice are viable and fertile, develop normally, and display no overt abnormalities. A comparison of the iron status of suckling offspring from LFKO(-/-) intercrosses and from wild-type (WT) intercrosses showed that lactoferrin is not essential for iron delivery during the postnatal period. Further, analysis of adult mice on a basal or a high-iron diet revealed no differences in transferrin saturation or tissue iron stores between WT and LFKO(-/-) mice on either diet, although the serum iron levels were slightly elevated in LFKO-/- mice on the basal diet. Consistent with the relatively normal iron status, in situ hybridization analysis demonstrated that lactoferrin is not expressed in the postnatal or adult intestine. Collectively, these results support the conclusion that lactoferrin does not play a major role in the regulation of iron homeostasis.

The physiology of lactoferrin

This paper reviews our current knowledge of the structure and function of the iron-binding protein lactoferrin. In particular, it attempts to relate the various proposed physiological functions of lactoferrin to its most characteristic biochemical properties, i.e. its ability to bind iron and its highly basic nature. The extent to which various physiological functions can be considered as definitely established is critically reviewed, and suggestions for future research are proposed.