Enzyme immunoassay of lactoferrin in newborn term infants: reference values and influence of diet

Transcriptomic analysis identifies lactoferrin-induced quiescent circuits in neonatal macrophages

Introduction

Upon birth, a hitherto naïve immune system is confronted with a plethora of microbial antigens due to intestinal bacterial colonization. To prevent excessive inflammation and disruption of the epithelial barrier, physiological mechanisms must promote immune-anergy within the neonatal gut. As high concentrations of human lactoferrin (hLF), a transferrin glycoprotein shown to modulate macrophage function, are frequently encountered in colostrum, its direct interaction with intestinal macrophages may satisfy this physiological need. Thus, the primary objective of this study was to investigate transcriptional changes induced by human lactoferrin in neonatal monocyte-derived macrophages.

Methods

Cord blood-derived monocytes were differentiated with M-CSF in presence or absence of 500 µg/mL hLF for 7 days and afterwards stimulated with 1 ng/mL LPS or left untreated. RNA was then isolated and subjected to microarray analysis.

Results

Differentiation of cord blood-derived monocytes in presence of hLF induced a distinct transcriptional program defined by cell cycle arrest in the G2/M phase, induction of IL-4/IL-13-like signaling, altered extracellular matrix interaction, and enhanced propensity for cell-cell interaction. Moreover, near-complete abrogation of transcriptional changes induced by TLR4 engagement with LPS was observed in hLF-treated samples.

Discussion

The global transition towards an M2-like homeostatic phenotype and the acquisition of quiescence elegantly demonstrate the ontogenetical relevance of hLF in attenuating pro-inflammatory signaling within the developing neonatal intestine. The marked anergy towards proinflammatory stimuli such as LPS further underlines the glycoprotein's potential therapeutic relevance.

Serum lactoferrin concentration of primiparous sow during gestation and lactation, and comparison between sow-fed and formula-fed piglets

Lactoferrin (LF) is a sialylated iron-binding glycoprotein, occurring in several biological secretions like milk, saliva, and seminal fluids and is a major component of a mammalian innate immune system. It plays multiple protective roles against large group of microorganisms and performs anti-inflammatory and anti-cancer activities. The concentration of serum LF in gilt (primiparous sow) and their piglets remains unknown. We determined serum LF concentration in gilts during gestation and lactation to that of 19-d-old piglets, including sow-fed and formula-fed piglets using enzyme-linked immunosorbent assay (ELISA). We found that the concentration of serum LF in gilts varied during gestation (0.77 ± 0.10 µg/mL) and lactation (0.62 ± 0.11 µg/mL). The mean concentration of serum LF in gilts (0.72 ± 0.06 µg/mL) was significantly higher than that of piglets (0.42 ± 0.07 µg/mL, P = 0.004). Additionally, a marginal significant difference (P =0.06) was observed for serum LF concentration in sow-fed piglets (0.42 ± 0.03 µg/mL) at 19 d old compared to that of formula-fed piglets (0.33 ± 0.04 µg/mL) at 37 d old. This study provides noble information regarding the serum LF concentration in the healthy gilts and piglets and thereby the data can be used as a standard reference point for future studies on the role of LF in pig reproduction.

Lactoferrin: a multifunctional glycoprotein

Lactoferrin is an iron-binding glycoprotein found in milk, exocrine secretions of mammals, and in secondary granules from polymorphonuclear neutrophils. This review describes the wide spectrum of functions ascribed to lactoferrin, with special emphasis on the antimicrobial properties of this protein, and its derived peptides.

Iron-saturated lactoferrin as a co-mitogenic substance for neonatal rat hepatocytes in primary culture

We studied the effect of lactoferrin on DNA synthesis in neonatal rat hepatocytes in primary culture to determine if this agent acts as a mitogen in human milk. Thymidine incorporation into the DNA of cultured hepatocytes stimulated by lactoferrin in the presence of insulin and human epidermal growth factor was examined. Iron-saturated lactoferrin increased DNA synthesis of neonatal hepatocytes by 1.5 times and this potency was the same as that of insulin. It significantly enhanced the stimulatory effect of human epidermal growth factor plus insulin; DNA synthesis under these conditions was seven times that of control. Iron-free lactoferrin did not affect DNA synthesis, nor did the exogenous addition of ferric ions. The enhancement of DNA synthesis by iron-saturated lactoferrin was significant for neonatal hepatocytes, but not for adult hepatocytes. These results suggest that iron-saturated lactoferrin, which itself had low mitogenic activity, is a co-mitogenic substance for neonatal hepatocytes in vitro.

An enzyme-linked immunosorbent assay for plasma-lactoferrin. Concentrations in 362 healthy, adult blood donors

Very different concentrations of plasma-lactoferrin in healthy adults have been reported in the literature. We compared three commercially available lactoferrins and lactoferrin purified in our laboratory as calibrators in an ELISA. No statistical differences among these preparations of lactoferrin were detected. The concentration of purified lactoferrin was measured by dry weight, and efforts were made in order to minimize loss of purified lactoferrin by adhesion to tubes etc. and thus, secure accuracy of the method. Dilutions were made in PBS 0.01 mol l-1 with NaCl 0.436 mol l-1, (NH4)2SO4 0.5 mol l-1, BSA 5 gl-1 and normal rabbit IgG 10 mg l-1, which was shown to give parallel dilution curves of primary calibrator, secondary calibrator and plasma samples. No significant difference in the content of lactoferrin in neutrophils (median; range) among men (1.78; 0.83-4.48 micrograms 10(-6) neutrophils; n = 20) and women (2.12; 1.16-9.30 micrograms 10(-6) neutrophils; n = 14) was found. Lactoferrin was analysed in EDTA-plasma obtained from 135 female and 227 male blood donors. Median concentrations were 84.7 and 97.8 micrograms l-1 respectively, while 2.5% and 97.5% reference limits (with 90% confidence intervals) were estimated to 42.9 (38.7-47.4) micrograms l-1 and 166.9 (151.0-186.3) micrograms l-1 for women and 52.3 (49.1-55.6) micrograms l-1 and 189.9 (175.9-206.4) micrograms l-1 for men, respectively.

Plasma lactoferrin levels in newborn preterm infants: effect of infection

Plasma lactoferrin was measured within 24 h of birth in 23 preterm infants of between 24 and 36 weeks gestation. Lactoferrin concentrations fell with decreasing gestational age whilst the incidence of subsequent infection rose. Sequential measurements on a subgroup of 10 preterm infants showed that even when initial lactoferrin concentrations were within the range for term infants, they fell during the first week. Lactoferrin concentrations in preterm babies may rise transiently, such increases often being associated with clinical signs of infection. A rise in plasma lactoferrin of 200 micrograms/L or more over a period of less than 48 h is suggestive of infection. These findings are discussed in terms of both the possible role of lactoferrin, and the clinical usefulness of the measurement.