Immunoreactive properties of α-casein and κ-casein: Ex vivo and in vivo studies

The aim of this study was to evaluate the ex vivo and in vivo studies immune potential of alpha- and kappa-casein. Ex vivo, naive mouse splenocytes were stimulated with alpha- or kappa-casein. After 120 h of culture, the proliferation index (PI), determined by 3-(4,5 dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and carboxyfluorscein diacetate N-succinimidyl ester (CFSE) staining, did not vary for either antigen, suggesting similar ex vivo immunogenic potential of both casein fractions. In vivo, BALB/ccmdb mice were sensitized with alpha- or kappa-casein and then gavaged with primary antigen. Mice immunized with alpha-casein had higher levels of IgG (2(16.33) ) and IgA (2(10.22)) in serum at the end of the experiment compared with mice immunized with kappa-casein (2(15) and 2(9.3) for IgG and IgA, respectively). The use of alpha-casein for mouse immunization and ex vivo lymphocyte stimulation resulted in higher concentrations of secreted cytokines (IL-4, IL-10) compared with kappa-casein stimulation. This is con sistent with increasing regulatory T cell (Treg) lymphocyte populations, independent of the antigen used for stimulation. In summary, the immunogenic potential of alpha- and kappa-casein was similar. Humoral and cellular immune responses confirmed their strong, independent potential to induce B and T cells. We propose that the lymphocyte proliferation index be used as an initial screening for protein immunogenicity.