This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Which immunoglobulin is present in the breast milk: September 2005 \nSelect and explain. \nA. Ig A, B. Ig E, C. Ig D, D. Ig M', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. A: Ig A Secretory IgA is the principal immunoglobulin of breast milk/colostrum. It is synthesized in the mammary epithelial cell by the coupling of two IgA molecules, produced locally by lymphocytes resident in the breast tissue, with two proteins, J-chain and secretory component. The specificity of breast milk secretory IgA antibodies reflects the mother's exposure to mucosal infection and is independent of the specificity profile of blood-borne IgA.", 'role': 'assistant'}]