Local immune complexes and inflammatory response in patients with chronic interstitial pulmonary disorders associated with collagen vascular diseases.

Evidence is accumulating that the lung injury in collagen vascular diseases (CVD) is triggered by immune complexes (IC). These reactions are neutrophil- and complement-dependent. The direct, in vivo phagocytosis of IC by bronchoalveolar lavage polymorphonuclear leucocytes (BAL-PMN), was studied in 15 patients with CVD and chronic interstitial pulmonary disorders. A control group (NC) consisted of nine healthy, non-smoking volunteers. Concentrations of soluble IC were measured using a solid phase Clq ELISA assay, and an indirect, in vitro phagocytosis assay performed using healthy donor PMN. Local Ig and C3 concentrations were determined using laser nephelometry and Mancini techniques, respectively. In the patient group the total cell counts/ml recovered lavage fluid and the proportions of BAL-PMN were significantly increased (P less than 0.05 and P less than 0.001, respectively). The influxed PMN showed high scores of direct IC phagocytosis. Soluble IC concentrations were significantly increased compared with controls (all comparisons P less than 0.01), and in the BAL relatively higher than in the serum of the same patients. Concomitantly high local IgG concentrations were observed. Corticosteroid treatment gave rise to significantly decreased total cell counts (P less than 0.05), and proportions of BAL-PMN (P less than 0.001), a decrease in the in vivo IC phagocytosis (P less than 0.05), in the indirect, in vitro IC phagocytosis, in the Clq ELISA and in the local IgG concentrations (all comparisons P less than 0.001). We concluded that locally formed IC may induce an inflammatory response in the lungs of patients with CVD.