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': 'Function of IgA is - \nSelect and explain. \nA. Acts as a mucosal barrier for infection, B. Circulating antibody, C. Kills virus infected cells, D. Activates macrophages', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Acts as a mucosal barrier for infection Secretory IgA is selectively concentrated in secretions and on mucus surfaces forming an 'antibody paste' and is believed to play an impoant role in local immunity against respiratory and intestinal pathogens.", 'role': 'assistant'}]