ABSTRACT
Pulmonary fibrosis is characterized by lung inflammation and abnormal tissue repair resulting in the replacement of normal functional tissue with an abnormal accumulation of fibroblasts and deposition of extracellular matrix in the interstitium and alveolar spaces. The process involves cellular interactions via a complex cytokine-signaling mechanism and heightened collagen gene expression, ultimately resulting in their abnormal deposition in the lung. Current understanding of the pathogenesis of pulmonary fibrosis suggests that in addition to inflammatory cells, the fibroblast and fibroblastlike cells (e.g., myofibroblasts) play important roles in the diverse processes that constitute fibrosis. Indeed, there is now mounting evidence to support the concept that the fibroblasts can be potent effector cells, releasing many of the same cytokines, as do the various inflammatory cells. Furthermore, in conjunction with its ability to elaborate extracellular matrix, the myriad activities of the cytokines produced by these cells would argue for active roles for this cell type in the response to tissue injury, inflammation, repair, and fibrosis.
