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 immunoglulin - \nSelect and explain. \nA. IgA, B. IgG, C. IgM, D. IgD', 'role': 'user'}, {'content': "Answer: A \nExplanation: Immunoglobulin A is an antibody that plays a critical role in immune function in the mucous membranes. More IgA is produced in mucosal linings than all other types of antibody combined Ref: Ananthanarayan & Parker's textbook of microbiology 9th edition pg:97-98", 'role': 'assistant'}]