Current understanding of the inflammatory process in cystic fibrosis: onset and etiology.
Although airway obstruction and chronic endobronchial infection have long been recognized as major factors in the pathogenesis of lung disease in cystic fibrosis (CF), only recently has it been recognized that the inflammatory process itself may be responsible in a major way for destroying the lungs. The most characteristic feature of inflammation in the CF lung is the persistent infiltration of massive numbers of neutrophils into the airways. Although neutrophils help to control infection, when present in great excess, they cause more harm than good. Major advances in our understanding of the inflammatory process in the CF lung have come from the use of bronchoscopy and bronchoalveolar lavage (BAL) to analyze the inflammatory process in patients who are relatively symptom free and/or do not regularly produce sputum. Recent BAL studies suggest that neutrophil-rich inflammation begins very early, even in infants without clinically apparent lung disease. A number of chemoattractants from epithelial cells, macrophages, neutrophils themselves, and bacterial products contribute to the neutrophil influx. Surprisingly, some infants have inflammation even in the apparent absence of infection, leading to the speculation that inflammation may precede infection. Links between the basic defect in CF and inflammation have been postulated, with dysregulation of cytokine production and abnormal epithelial host defenses being implicated as causal factors of sustained inflammation. Regardless of the details of how this process is initiated and/or perpetuated, it has become clear that inflammation begins at a very early stage and progresses throughout life, gradually worsening and destroying the lungs. For these reasons, anti-inflammatory therapy should be initiated in early life. Additional studies are necessary to define the optimal antiinflammatory drugs and regimens, and to confirm their long-term safety and efficacy.