Alpha-LA is the B protein of lactose synthetase secreted by the mammary epithelial cells. a-LA is a potent Ca(2+)-elevating and apoptosis-inducing agent with broad, yet selective, cytotoxic activity. Multimeric a-LA kills all transformed, embryonic, and lymphoid cells tested but spared mature epithelial elements. It suggests that milk contributes to mucosal immunity not only by furnishing antimicrobial molecules but also by policing the function of lymphocytes and epithelium. a-LA may be helpful in ascertaining the site of origin of metastatic breast tumors
