This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'In respiratory and GIT infections, which is the most affected immunoglobulin? \nSelect and explain. \nA. IgA, B. IgG, C. IgM, D. IgD', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., IgA(Ref: Ananthanarayan,9th/e, p. 97 - 98 and 8th/e, p. 98 - 99)* IgA (Secretory IgA) is selectively concentrated in secretions and on mucous surfaces forming an antibody paste and is believed to play, an important role in local immunity against respiratory and intestinal pathogens.", 'role': 'assistant'}]