Complement Activation in Cystic Fibrosis Respiratory Fluids: in Vivo and in Vitro Generation of C5a and Chemotactic Activity

Abstract

ABSTRACT. Experiments performed in vitro have demonstrated that leukocyte neutral proteases produce an important mediator of inflammation, C5a, by proteolysis of the C5 component of the complement system. Cystic fibrosis (CF) lung fluids were characterized by high levels of neutrophils (39% of total cells versus 2% in normals) and contained significantly elevated amounts of elastolytic activity (mean 17.7 ng/pg total protein) compared to the lung fluids obtained from normal volunteers (0.2 ng elastolytic activitylpg protein, p = 0.001). The objective of these studies was to determine if complement activation and complement-derived chemotactic activity are present in CF lung fluids. C3c peptide representing activation of C3 could not be identified in the bronchial-alveolar lung lavage fluids of normal subjects but was readily identified by means of crossed immunoelectrophoresis "in CF lung fluids (n = 9, mean 49% of C3); the mean level of C3 was decreased in CF lung specimens. Chemotactic activity was significantly elevated in lung fluids of the CF patients when compared to normal lung fluids. Using gel-filtration chromatography and a sensitive radioimmunoassay the chemotaxin present in CF specimens was identified as the anaphylatoxin C5a. C5a levels in the bronchial-alveolar lavage fluids of CF patients was inversely related to volume in liters expired in 1 s of a forced expiratory maneuver expressed as a percent of vital capacity determined from a forced expiratory maneuver ( r = -0.72). Because there was a direct relationship between the total elastolytic activity present in CF airways and the concentration of C5a ( r = 0.97, p = 0.03), it was postulated that airway proteases with elastolytic activity also cleave C5, nonimmunologically producing C5a. Detailed inhibition assays revealed that much of the total elastolytic activity had the inhibition profile of a serine proteinase. The levels of the serine proteinases were closely correlated with the numbers of neutrophilic leukocytes present per ml of lavage fluid ( r = 0.7, p = 0.05).However, inhibitors of leukocyte serine proteases did not prevent the generation of additional chemotactic activity

Immunization with aPseudomonas aeruginosaElastase Peptide Reduces Severity of Experimental Lung Infections Due toP. aeruginosaorBurkholderia cepacia

“…Pulmonary infection by P. aeruginosa in CF patients is followed by an inflammatory response characterized by an influx of PMNL into the lung [31]. To determine the effects of immunization with the peptide epitopes on lung inflammation, we performed lavage on groups of animals on PI days 3 and 7, and the total cell number, neutrophil number, protein concentration, and NE-like activity were determined in the BAL fluid.…”

Decreased polymorphonuclear leucocyte chemotactic response to leukotriene B4 in cystic fibrosis

“…This abnormality was not demonpatients with CF and chronic Ps. aeruginosa infection [3][4][5]7,29]. strated with two unrelated chemotactic stimuli, which is However, the relative importance of C~a-and LTB4-induced consistent with a specific decrease of receptor-mediated re-PMN responses in the airways of patients with CF is uncertain.…”

“…There is evidence that C5a is degraded rapidly in sputum by proteases of bacterial and/ or host cell origin [5,29]. Local eicosanoid production is therefore likely to be important in the disease process in vivo.…”

Generation and Metabolism of Leukotrienes in Granulocytes of Patients with Cystic Fibrosis

“…Although the genetic defect has recently been elucidated [3], the precise mechanism leading to chronic obstruction of the airways and initiating a life-threatening cascade of inflammatory processes remain unclear [4,5]. The gradual destruction of the regular lung structure and function is associated with the release of proinflammatory substances in the bronchoalveolar space, such as elastase, complement components (C5a), oxygen radicals, immune com plexes, as well as low molecular weight mediators, indicating the activation of several processes in the immune system [6][7][8].…”