Immunomodulating effects of whey proteins and their enzymatic digests

Immunomodulating properties of commercial whey protein products and their enzymatic digests (trypsin/chymotrypsin) were evaluated by measuring their effect on in vitro proliferation of lymphocytes isolated from murine spleen. The results showed that microfiltered-whey protein isolates (MF-WPI) significantly increased lymphocytes proliferation at a concentration of 100 mug mL(-1). An inhibitory effect was measured for lactoferrin at the same concentration, while no effect was observed for ionic exchange-WPI, beta-lactoglobulin, a-lactalbumin, and glycomacropeptide. Enzymatic digestion of protein products abrogated the inhibitory effect of lactoferrin and reduced the stimulating effect of MF-WPIs. However, fractionation by isoelectric focusing of the MF-WPI enzymatic digests led to peptide fractions that stimulated cells proliferation at much lower concentrations (0.5-500 mug mL(-1)) than the ones obtained for the total hydrolysates (2000 mug mL(-1)). The results suggest that whey proteins contain some immunomodulating peptides, which can be released by enzymatic digestion. Identification and isolation of these bioactive peptides could provide insights into the preparation of potent immunomodulating products. (C) 2003 Elsevier Ltd. All rights reserved.