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. Interferonγ production of human PBL was also accelerated 6.0-fold by 50 μg/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°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.