[The role of lactoferrin in the proper development of newborns].

Colostrum and milk contain, in addition to nutritional constituents, also proteins crucial for the normal development of the offspring. Lactoferrin (LF) belongs to the family of iron-binding proteins and exhibits a wide spectrum of antimicrobial and immunotropic properties. LF is particularly resistant to proteolytic degradation in alimentary tract, in contrast to other milk proteins, e.g. casein. In any case, LF-derived peptides also possess potent antibacterial activities. LF is absorbed from the intestine by means of specific receptors located on brush border cells. Administered orally, LF stimulates both local and systemic immune response. LF plays a role in the absorption of nutrients. The protein can deliver such metal ions as iron, manganese, and zinc and facilitate the absorption of sugars. LF stimulates the proliferation of gut endothelial cells and the growth of gut-associated lymphatic follicles. This property suggests the possibility of applying LF in premature infants and patients with damaged intestinal mucus. LF controls the proper composition of the gut microflora. It suppresses the growth of pathogenic bacteria while promoting the multiplication of nonpathogenic Lactobacillus and Bifidobacterium. Newborns fed an artificial diet develop harmful microflora (Enterococcus, Enterobacter, Bacteroides, Escherichia). The non-pathogenic microflora ensures low pH, produces some vitamins, increases the activity of NK cells, T lymphocytes, and macrophages, promotes the production of protective immunoglobulins, and lowers the risk of allergies. In studies on mice, LF was found to be protective in bacteremia and endotoxemia. The protein stimulates the activity of reticulo-endothelial system cells and elicits myelopoiesis, thus increasing the killing and clearance of bacteria. In the model of experimental endotoxemia, LF inhibits the activity of pro-inflammatory cytokines, nitric oxide, and reactive forms of oxygen. LF can also promote the differentiation of T and B cells from their immature precursors and increases the activity of NK and LAK cells. It also protects against the toxicity of reactive oxygen radicals. This property may be particularly relevant when baby food, based on modified cow's milk, contains mineral iron, which may be a source of harmful free radicals. In summary, it is obvious that natural human milk has the best value for newborns. Supplementation of artificial baby food with LF seems essential to improve the protective and immunoenhancing property of this kind of diet. It is clear that cow's milk is not appropriate for human newborns. Cow's milk contains 50 times less LF, only traces of lysozyme, and lower concentrations of other whey proteins and immunologically relevant immunoglobulins. Therefore commercially available baby foods (United States, Japan) are supplemented with LF.