Antibodies raised against bovine beta-lactoglobulin react with beta 2-microglobulin. A possible antigenic region at...

beta-Lactoglobulin is a major whey protein in bovine milk. Its presence has been demonstrated in all mammals examined except rodents and humans. However a positive cross reaction was observed for human milk proteins with antibodies raised against bovine beta-lactoglobulin. We isolated and characterized a protein fraction of ca. 12 kDa responsible for the positive cross reaction. N-terminal sequencing and amino-acid analysis indicated that this protein is identical with human beta 2-microglobulin. We observed structural homology between beta-lactoglobulin region 124-140 and beta 2-microglobulin 71-86, which suggested that positions 124-140 could be the antigenic region for beta-lactoglobulin. Six highly conserved amino-acid residues are suggested as candidates for the antigenic site.