Lactoferrin (Lf) is a milk iron-binding glycoprotein that plays a role in iron transport and acts as both a bacteriostatic and a growth modulating agent. The aim of this study was to investigate the nature of immune responses induced by repeated oral administration of bovine milk Lf in mice. Groups of ten female BALB/c mice were fed daily for 4 weeks with two doses of protein antigen: a low (0·05 mg/g body weight per d) or high (1 mg/g body weight per d) dose of Lf, or water as a control. A fourth group was immunized intramuscularly with 0·01 mg Lf in complete Freund's adjuvant. Anti-Lf IgA and IgG were detected in the intestinal fluid and serum of mice given Lf. Total immunoglobulins were higher in the intestinal fluid in Lf groups than in the control group. No difference could be detected in the serum. IgA and IgG secretion was enhanced in Peyer's patches and spleen from Lf-fed mice, in comparison with controls. [3H] thymidine uptake into Peyer's patch and spleen cells from both control and Lf-fed mice was enhanced by 75 μg Lf/ml in vitro, but Lf groups had a greater proliferation rate than the control group. These findings suggested that Lf could act as an immunostimulating factor on the mucosal immune system and that activation of the mucosal immune system is dependent on the ability of Lf to bind to the intestinal mucosa.

No abstract

Food protein intake interacts with the immune system. In earlier nutritional and immunological studies, nutrients, particularly milk whey proteins, were generally administered in soluble form and by gavage. However, orogastric intubation does not represent a natural way of ingesting nutrients such as lactoferrin (Lf). We examined how different modes of oral administration of Lf could affect the regulatory effect of this molecule on intestinal and systemic immune responses. Groups of 10 female BALB/c mice were administered Lf daily for 6 wk. To address the influence of the oral modes of administration, mice were given Lf either in solution, by gastric intubation or in the drinking water, or as a powder, by buccal deposition or in the diet. Mucosal and systemic immune responses, including specific immunoglobulin (Ig) secretion, cell proliferation, and cytokine production, were analyzed and compared with those of naïve mice given water under the same conditions or positive control mice that were administered Lf by i.m. injection. The addition of Lf to the drinking water had no visible effect on the immune status. Gastric intubation, single buccal doses, and continuous doses of Lf in the diet stimulated transient systemic and intestinal antibody responses against Lf. All of these oral modes of Lf exposure biased mucosal and systemic T-cell responses toward Thelper (Th)2-types and elevated IgA production by mucosal cells. However, the less natural gastric intubation also promoted Th1-type responses as evidenced by serum IgG(2a) antibodies and the secretion of Th1 cytokine by mucosal and systemic T cells in vitro. Thus, one should carefully consider the oral mode of administration for understanding regulation of immune responses by food proteins such as Lf.

This study was designed to analyse the effects of human (h) and bovine lactoferrin (bLF) on the growth and differentiation of intestinal cells using the mice model supplemented with Lactoferrin (LF) and the enterocyte-like model of Caco-2 cells which spontaneously differentiate after confluency. In mice, bLF supplementation increased jejunal villus height and the expression of several intestinal brush border membrane enzymes activities. Addition of bLF or hLF to undifferentiated Caco-2 cells was able to increase cell proliferation with confluency being reached more rapidly. Moreover, when Caco-2 cells were grown in the presence of LF for 3 weeks, brush-border membrane-associated enzyme activities i.e. sucrase, alkaline phosphatase and neutral aminopeptidase, as well as the L-glutamate transporter expression were all increased indicating an increased Caco-2 cell differentiation. Accordingly, cDNA Atlas array and Western blot analysis of cell cycle proteins shown a decreased expression of Cdck2 and an increased TAF1 expression; these proteins being implicated in the regulation of numerous genes related to cellular proliferation and differentiation. These modifications were associated with an inhibition of Caco-2 cell spontaneous apoptosis. Altogether, our results indicate that LF increase in vivo and in vitro enterocyte differentiation. In addition, LF was found to increase in vitro enterocyte proliferation resulting in higher cell density in cell flasks, an effect that was likely partly due to a reduction of the cellular apoptosis. The different stimulation patterns observed for the different parameters associated with cell differentiation in relationship with specific gene regulation is discussed.