Bovine milk-derived products, in particular whey proteins, exhibit beneficial properties for human health, including the acquired immune response. However, their effects on innate immunity have received little attention. Neutrophils are key cells of innate defenses through their primary functions of chemotaxis, phagocytosis, oxidative burst, and degranulation.
A whey protein extract (WPE) purified from bovine lactoserum was evaluated for its direct and indirect effects on these primary functions of normal human blood neutrophils in vitro. Although WPE had no direct effects on primary functions, a 24-h pretreatment of neutrophils with WPE was associated with a significant and dose-dependent increase of their chemotaxis, superoxide production, and degranulation in response to N-formyl-methionine-leucine-phenylalanine, as well as of their phagocytosis of bioparticles. The pretreatment increased the surface expression of CD11b, CD16B, and CD32A receptors. The major WPE protein components b-lactoglobulin (b-LG) and a-lactalbumin (a-LA) were the main active fractions having an additive effect on human neutrophils that became more responsive to a subsequent stimulation. This effect on NADPH oxidase activity was associated with translocation of p47phox to plasma membrane. Glycomacropeptide, a peptide present in measurable amounts in WPE products, was able to enhance the individual effect of b-LG or a-LA on neutrophils. The present data suggest that WPE, through b-LG and a-LA, has the capacity to enhance or ‘‘prime’’ human neutrophil responses to a subsequent stimulation, an effect that could be associated with increased innate defenses in vivo.