Suppression of lymphocyte proliferation in vitro by bovine caseins hydrolyzed with Lactobacillus casei GG-derived enzymes.
BACKGROUND: Processing of proteins in the gut and activation of T-cell suppression leads to systemic hyporesponsiveness to ingested protein antigens. OBJECTIVE: The study was designed to determine whether lactobacilli, a major part of human intestinal microflora, can contribute to degradation of food antigens in the gut and modify their immunoactivities. METHODS: Lymphocyte transformation tests were carried out in healthy adults to determine the mitogen-induced lymphocyte proliferative responses to bovine caseins hydrolyzed with pepsin and trypsin and to bovine caseins additionally hydrolyzed with enzymes derived from Lactobacillus casei strain GG (ATCC 53103). RESULTS: In experiments done with caseins hydrolyzed with pepsin and trypsin, beta- and alpha(s1)-caseins significantly suppressed the proliferation of lymphocytes at 0.1 and 10 micrograms/ml, respectively, when compared with corresponding control cultures without these hydrolysates. In contrast, kappa-casein significantly stimulated the proliferation of lymphocytes at 10 micrograms/ml. In experiments done with caseins additionally hydrolyzed with L. casei GG-derived enzymes, there was one consistent effect on lymphocyte proliferation: suppression by alpha(sl)-, beta-, and kappa-caseins at 0.1, 10, and 1000 micrograms/ml, respectively. CONCLUSIONS: Hydrolysis of caseins with L. casei GG-derived enzymes generates molecules with suppressive effects on lymphocyte proliferation. In addition, intestinal bacteria can be beneficial in the downregulation of hypersensitivity reactions to ingested proteins in patients with food allergy.