STUDIES ON THE ANTIGENICITY OF COW KAPPA-CASEIN

Analysis of a quantitative precipitation of cow k-casein with its rabbit antiserum indicated that there were at least 5 antigenic determinants on cow k-casein molecule. On immunodiffusion analysis and in a two-step inhibition test involving an enzyme-linked immunosorbent assay, reduced S-carboxymethylated cow k-casein reacted with antibodies against k-casein as well as untreated k-casein. On the other hand, to study the antigenic property of cow k-casein, peptide fragments 1-95, 96-106 and 107-169 were separated from k-casein cleaved with cyanogen bromide, and the antigenic reactivities of the peptide fragments with rabbit IgG, human IgG and human IgE antibodies against cow k-casein were examined. In an enzyme-linked immunosorbent assay, all peptide fragments reacted noticeably with rabbit IgG, human IgG and human IgE antibodies. Moreover, on immunodiffusion analysis using rabbit antibody, peptide fragments 1-95 and 107-169 formed a single and sharp precipitin arc. These results indicate that at least 3 antigenic determinants are associated with each of regions 1-95 and 107-169, and at least one with region 96-106.