MONONUCLEAR-CELLS IN EXUDATIVE MALIGNANT PLEURAL EFFUSIONS - CHARACTERIZATION OF PLEURAL PHAGOCYTIC-CELLS

The aims of this study were to develop a methodology for the isolation of highly enriched mononuclear phagocyte populations from exudative m alignant pleural effusions (EMPE) and to characterize the phenotype an d functional properties of these cells. Pleural effusion mononuclear c ells (PEMC) were isolated by Ficoll centrifugation of EMPE and transud ative pleural effusions and allowed to adhere to plastic for 1 hto obt ain a pleural effusion mononuclear adherent cell (PEMAC) fraction. Onl y 66.0 +/- 4.2 percent of PEMAC ingested latex particles, indicating t hat a significant proportion of PEMAC were not phagocytic cells. Latex -positive PEMAC had the morphologic appearance of macrophages and stai ned positive (97.3 +/- 4.3 percent) with the anti-CD68 monoclonal anti body (MoAb), specific for macrophages. Conversely, latex-negative PEMA C (34.0 +/- 4.1 percent of PEMAC) did not react with the anti-CD68 MoA b and stained with anti-CDS (34.7 +/- 10.7 percent) and anticytokerati n (50.5 +/- 16.4 percent) MoAbs, indicating that T cells and mesotheli al cells were present in the PEMAC fraction. To improve the purificati on of pleural macrophages, PEMAC were cultured for an additional 18 h and the cells that remained adherent after this period constituted the firmly adherent mononuclear cell (FAMC) fraction. Nearly 90 percent o f FAMC ingested latex particles and were CD88-positive. Virtually all FAMC were CD3-negative and cytokeratin-negative. Similar percentages o f FAMC from EMPE and transudative effusions expressed the monocyte-lin eage markers CD11b and CD14, suggesting that the proportion of monocyt e-like mononuclear phagocytes in the pleural space is not increased du ring local tumor-associated inflammatory responses. The FAMC from EMPE (1) expressed HLA-DR antigens, (2) released interleukin 1(IL-1)beta a nd tumor necrosis factor (TNF) alpha, and (3) stimulated allogeneic T- lymphocyte proliferation. The results of this study suggest that pleur al mononuclear phagocytes may be involved in tumor-associated inflamma tory reactions in the pleural compartment by stimulating the prolifera tion of other and by releasing inflammatory inflammatory cytokines.