Phenotypic and functional characterization of normal rat pleural macrophages in comparison with autologous peritoneal and alveolar macrophages

Pleural mononuclear phagocytes (PleMP) were isolated from normal rats by pl eural lavage and compared with autologous peritoneal (PerMP) and bronchoalv eolar mononuclear phagocytes (BAMP) isolated by peritoneal and bronchoalveo lar lavage, respectively. The phagocytic activity of PleMP, PerMP, and BAMP , evaluated by testing their ability to ingest latex beads, was lower for P leMP and PerMP than for BAMP. The phenotype of PleMP, PerMP, and BAMP was c haracterized by immunocytochemical staining with a panel of monoclonal anti bodies (mAbs). As expected, PleMP, PerMP, and BAMP did not react with OX19, OX33, ED5, MOM/3F12/F2, and anticytokeratin mAbs, specific for T lymphocyt es, B lymphocytes, dendritic cells, granulocytes, and epithelial/mesothelia l cells, respectively. Moreover, PleMP and PerMP populations were highly en riched with OX6-, OX42-, ED7-, and ED8-positive MP, whereas BAMP population was enriched with ED1- and ED9-positive cells. To test the ability of PleM P, PerMP, and BAMP to function as accessory cells (AC), mitomycin C-treated MP were used as stimulatory cells in mixed leukocyte reaction experiments, using allogeneic T cells as responders. (3)HdTR incorporation by T cells w as assessed as an index of AC function. PleMP and PerMP were more potent AC than BAMP. Moreover, when cultured together with autologous pulmonary inte rstitial dendritic cells, PleMP and PerMP exerted a more potent ability to stimulate T-cell proliferation than did BAMP. To investigate the capacity o f MP to function as bactericidal and fungicidal cells, we tested their abil ity to kill Escherichia coli and Cryptococcus neoformans, respectively. Ple MP and PerMP were less potent bactericidal and fungicidal cells than BAMP. The results of this study demonstrate that PleMP isolated from normal rat p leural space are functionally and phenotypically different from BAMP but si milar to PerMP, and suggest that these cells might play an important role i n cell-mediated immune reactions in the pleural space.