RECRUITMENT OF INFLAMMATORY CELLS TO THE PLEURAL SPACE - CHEMOTACTIC CYTOKINES, IL-8, AND MONOCYTE CHEMOTACTIC PEPTIDE-1 IN HUMAN PLEURAL FLUIDS

Pleural effusions secondary to various diseases are associated with th e presence of different inflammatory cells. The role of selective chem otactic cytokines in the recruitment of phagocytes to the pleural spac e is unclear. IL-8 and monocyte chemotactic peptide-1 (MCP-1) are rece ntly described cytokines that are chemotactic for neutrophils and mono cytes, respectively. We prospectively studied 63 patients, using stric tly defined criteria for their selection. IL-8 concentrations were ele vated in both empyema fluid (9.15 +/- 0.89 ng/ml) and parapneumonic ef fusions (4.7 +/- 0.697 ng/ml) when compared with pleural effusions sec ondary to other diseases. IL-8 levels were higher in empyema fluid tha n in parapneumonic effusions (p = 0.01). There was a significant corre lation between IL-8 levels and the total numbers of neutrophils in emp yema fluids (r = 0.80). Chemotactic activity for neutrophils was eleva ted in empyema fluid and the addition of IL-8 neutralizing serum decre ased bioactivity by 32.22%. Malignant pleural effusions had the highes t levels of MCP-1 (12.0 +/- 3.7 ng/ml) when compared with others. Cyto logy-positive pleural fluids (n = 10) had a higher level of MCP-1 than cytology-negative effusions (p = <0.05). Malignant pleural fluid MCP- 1 levels correlated (r = 0.70) with the absolute number of monocytes i n the pleural fluid. Neutralization of monocyte chemotactic activity o f malignant pleural fluid by specific neutralizing serum caused a 70.3 % inhibition of bioactivity. Immunohistochemical staining of malignant pleural fluid localized antigenic MCP-1 to malignant cells. We conclu de that both IL-8 and MCP-1 play major but not exclusive roles in the recruitment of neutrophils and monocytes from the vascular compartment to the pleural space.