A 12-month-old boy is brought to the physician for a follow-up examination. He just completed a course of antibiotics for a pneumonia one week ago. He has three episodes of pneumonia since birth and had chickenpox at the age of 7 months. White cell differential is normal. Examination shows oral thrush. CD4 count is 250/μL (NR >500). Abnormality of which of the following is the most likely explanation for these findings?
Common gamma chain
NADPH oxidase
Phagolysosomal fusion
Pharyngeal pouches
Tyrosine kinase
