Does beta-lactoglobulin occur in human milk?

Although beta-lactoglobulin (beta-lg) has been considered to be absent from human milk, recent results of other workers, based on immunological reactions between human milk and rabbit antiserum to bovine beta-lg, suggest that this protein may be present. Although our results show similar immunological reactions, we consider that lactoferrin is responsible for these, as it was the only reactive protein species which could be prepared to homogeneity. Indeed two types of antibodies were found by ELISA test in the antisera to bovine beta-lg. One of them would be able to bind loosely to human lactoferrin, but its binding sites would not be antigenic in the rabbit.