This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
[{'content': 'Deficiency of purine nucleoside phosphorylase causes \nSelect and explain. \nA. Complement deficiency, B. Cellular immunodeficeincy, C. Humoral immunodeficeincy, D. Combined immunodeficeincy', 'role': 'user'}, {'content': 'Answer: B \nExplanation: A combined T cell and B cell immunodeficiency that is a rare autosomal recessive metabolic disorder that has material basis in mutation in the PNP gene and characterized mainly by decreased T-cell function. Ref-Sathyanarayana 4/e', 'role': 'assistant'}]