Similarities of antisera to casein and epithelial membrane antigen.

Antisera raised against human milk fat globule membranes and against the casein fraction of human milk have been compared. Using an immunohistochemical stain of tissue sections it has been shown that many of the antigenic determinants detected by the different antisera are identical. A radioimmunoassay for epithelial membrane antigen (EMA) showed that casein preparations are associated with small quantities of EMA. Antisera to casein frequently contained appreciable concentrations of antibodies to EMA and this accounts for the immunohistochemical staining of non-mammary tissues.