Enhancement of immunoglobulin A formation by a casein phosphopeptide, bovine β-casein (1-28), via modulation of cytokines produced by Th2 type of lymphocytes in mouse spleen cell cultures

The effect of bovine beta-casein (1 -28) with a phosphoserine-rich region on the production of immunoglobulin (Ig) A and formation of cytokines such as interleukine (IL)-2, IL-4, IL-5, IL-6, IL-1 2 and interferon (IFN)-gamma was investigated in mouse spleen cell cultures. Two nanomoles of beta-casein (1-28) significantly enhanced secretion of IgA. The phosphopeptide was confirmed to stimulate significantly secretions of IL-5 and IL-6 in the presence and/or absence of the T lymphocyte mitogen. On the other hand, the level of immunoglobulin, in particular IgA, was significantly reduced when anti-IL-5 and/or anti-IL-6 antibodies were added to the cell cultures simultaneously with beta-casein (1-28). These results indicate that the casein phosphopeptide stimulates the formation of IL-5 and IL-6, suggesting that the cytokines are attributable to an increase in the IgA level in mouse spleen cell cultures with the phosphopeptide.