Immunostimulation of Murine Spleen Cells by Materials Associated with Bovine Milk Protein Fractions

Purified bovine milk proteins that were added to cultures of murine spleen cells significantly increased cell proliferation and production of immunoglobulin M. Casein and a whey mixture consisting of α-lactalbumin, bovine serum albumin, bovine gamma globulin, and β-lactoglobulin (β-LG) were stimulatory. Of the three β-LG preparations that are commercially available (β-LG containing variants A and B, purified variant A, and purified variant B), the unseparated mixture containing both the A and B variants showed the most immunomodulatory activity. Both alkaline treatment and trypsin digestion of the β-LG preparation markedly reduced its effectiveness. Polymyxin B, while greatly diminishing the stimulatory effect of lipopolysaccharide, had no significant effect on either the enhancement of cell proliferation or the enhancement of immunoglobulin production by β-LG. In the presence of S-(n-butyl)-homocysteine sulfoxamine, the stimulatory effect of β-LG on cell proliferation and IgM production in vitro was markedly reduced.