Immunomodulatory activity of beta-casein permeate medium fermented by lactic acid bacteria.

During fermentation, lactic acid bacteria may be able to release components that possess immunomodulatory activity. This activity was investigated in several culture supernatants arising from lactic acid bacteria cultured in a medium composed primarily of UF permeate of bovine milk; beta-CN was added as the sole protein source. Only a Lactobacillus helveticus supernatant allowed the modulation (both suppression and enhancement) of lymphocyte proliferation in vitro on human peripheral blood lymphocytes, but L. helveticus did not modulate the cytotoxic activity of natural killer cells or of lymphokine-activated killer cells. The addition of different quantities of culture supernatant to cultures of human mononuclear cells, stimulated by the mitogen concanavalin A, significantly increased the production of interferon-gamma and decreased the production of interleukin-2 and the expression of the alpha-chain of the interleukin-2 receptor (p55), all of which appear to be correlated with the decrease in lymphocyte proliferation. Our results suggest that the culture supernatant activity might be related to interaction with monocyte-macrophage and T helper cells, especially Th1-like cells.