<s>[INST] context: Bronchoalveolar lavage in patients with idiopathic pulmonary fibrosis, a chronic inflammatory disorder of the lower respiratory tract characterized by dyspnea and reticulonodular infiltrates on chest radiography, discloses an abundance of alveolar macrophages. Probably related to locally generated immune complexes, alveolar macro phages become activated and then produce several mediators that recruit and induce fibroblast proliferation, which causes secondary damage. Macrophage-derived mediators believed to be important in this process include fibronectin, a 200-kDa dimeric glycoprotein that interacts with connective tissue matrix as well as specific receptors on fibroblasts, and platelet-derived growth factor, whose chain is encoded by the c-sis protooncogene. Platelet-derived growth factor is believed to play an important role in recruiting fibroblasts to the site of inflammation. Macrophages also producechemotaxins such, as leukotriene 84 and interleukin 8, which attract neutrophils and eosinophils into the region. [/INST] question: The primary pathophysiologic problem in in idiopathic pulmonary fibrosis is believed to be | options: A: Microorganism mediated activation of pulmonary neutrophils B: Immune complex mediated activation of alveolar macrophages C: Direct immune complex mediated pulmonary interstitial damage D: Primary fibroblast | answer: B </s>