A 67-Year-Old Man Comes to the Physician Because of a 3-Month

A 67-year-old man comes to the physician because of a 3-month history of increasing shortness of breath on exertion, dry cough, and fatigue. He has a history of silicosis that was diagnosed 10 years ago. He has a recent fevers and night sweats. He worked in a glass manufacturing factory for 15 years and retired 2 years ago. Pulmonary examination shows diffuse crackles with right upper lobe predominance. An x-ray of the chest shows diffuse, small nodules; hilar adenopathy with prominent calcifications; and a cavitary lung lesion in the right upper lobe.. A sputum sample is sent for appropriate staining and culture.  This patient's increased susceptibility to the current infection is best explained by which of the following factors?

A) Extensive pulmonary fibrosis
B) Impaired immunoglobulin G response
C) Impaired macrophage function
D) Impaired type 2 helper T cell function
E) Ineffective mucociliary clearance