input: The following are multiple choice questions (with answers) about medical knowledge.   **Question:** A 6-month-old boy is brought to the physician by his parents for difficulty breathing and bluish discoloration of the lips for the past hour. During the past 3 months, the patient has had several upper respiratory tract infections and poor weight gain. Physical examination shows crackles over both lung fields and enlargement of the tonsils and cervical lymph nodes. His serum IgA, IgE, and IgG titers are decreased. An x-ray of the chest shows bilateral interstitial infiltrates. Methenamine silver staining of bronchial lavage fluid shows disc-shaped cysts. A defect in which of the following is the most likely underlying cause of this patient's condition?   (A) Actin filament assembly   (B) T-cell receptor signaling   (C) Microtubule polymerization   (D) B-cell maturation
output: ['(B) T-cell receptor signaling <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Actin filament assembly  (B) T-cell receptor signaling  (C) Microtubule polymerization  (D) B-cell maturation <> possible answers', "  A 6-month-old boy is brought to the physician by his parents for difficulty breathing and bluish discoloration of the lips for the past hour. During the past 3 months, the patient has had several upper respiratory tract infections and poor weight gain. Physical examination shows crackles over both lung fields and enlargement of the tonsils and cervical lymph nodes. His serum IgA, IgE, and IgG titers are decreased. An x-ray of the chest shows bilateral interstitial infiltrates. Methenamine silver staining of bronchial lavage fluid shows disc-shaped cysts. A defect in which of the following is the most likely underlying cause of this patient's condition? <> context"]