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
Deficiency of purine nucleoside phosphorylase causes 
Select and explain. 
A. Complement deficiency, B. Cellular immunodeficeincy, C. Humoral immunodeficeincy, D. Combined immunodeficeincy
B: Cellular immunodeficeincy
Answer: B: Cellular immunodeficeincy 
Explanation: 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