Immunomodulating properties of a whey protein isolate, its enzymatic digest and peptide fractions

A whey protein isolate (WPI) was hydrolysed using a mixture of trypsin:chymotrypsin, and the resulting enzymatic digest (ED) was separated into three peptide fractions by isoelectric focusing. The WPI, ED, and peptide fractions were tested for their immunomodulating effects using murine splenocytes cultured in the absence and presence of concanavalin A (ConA). The WPI, ED, and peptide fractions all stimulated the proliferation of splenocytes in the presence and absence of ConA, with the exception that WPI inhibited proliferation at high concentrations in the presence of ConA. The WPI and the ED had no effect on the secretion of Th1 (IL-2, IFN-γ) and Th2 (IL-4, IL-10) cytokines by resting splenocytes, while the peptide fractions significantly stimulated the secretion of IL-2 and IFN-γ. WPI inhibited ConA-induced cytokine secretion, whereas the ED and peptide fractions significantly increased IFN-γ secretion. Acidic or neutral peptide fractions stimulated splenocyte proliferation and cytokine secretion the most.