New aspects of hypersensitivity pneumonitis

PURPOSE OF REVIEW: Hypersensitivity pneumonitis (HP) represents a complex pulmonary disorder of varying intensity and clinical presentation, which is characterized by a diffuse Tc1 immune response of lung parenchyma and airways in patients previously sensitized to one of more than 300 etiologic agents that may favor the HP reaction. This review describes recent data that have clarified some of the events that govern the development of the hypersensitivity reaction following exposure to the causative agents involved in this disease. RECENT FINDINGS: A number of recent data clearly demonstrate that several cytokines and chemokines, which are secreted at sites of disease activity, participate in the pulmonary inflammatory responses taking place in the lung of patients with HP. SUMMARY: The past few years have seen outstanding advances in the understanding of immunologic and molecular events involved in the pathogenesis of HP. It is possible that these data could allow the discovery of therapeutic targets in individuals chronically exposed to HP antigens and evolving towards pulmonary fibrosis.