Immunostimulation effect of the fermented milk on human hybridomas and peripheral blood lymphocytes

Fat-free bovine milk fermented by more than 10 kinds of various lactic acid bacteria and yeast enhanced monoclonal antibody production of human hybridoma HB4C5 cells 2.8-fold in serum-free medium. Immunoglobulin production of human peripheral blood lymphocytes (PBL) was also stimulated in vitro. IgM and IgG production of human PBL was accelerated up to 2.8-fold and 5.4-fold, respectively. Interferon-gamma production of human PBL was also accelerated 6.0-fold by 50 mu g/ml of the fermented milk. However, interleukin-4 production of PBL was not affected. The activity was enhanced 2.5-fold by the thermal treatment for 30 min at 65 degrees C, and was completely lost by trypsin digestion. The findings suggested that the active substance in the fermented milk was heat stable protein. Gel-filtration and the SDS-PAGE analysis revealed that the molecular weight of the active protein, which was not detected in fat-free bovine milk before fermentation, was 19.0 kDa.