Opposite cellular accumulation and nitric oxide production in vivo after pleural immunization with M-leprae or M-bovis BCG

Mycobacteria as intracellular pathogens have evolved mechanisms to survive within macrophages. Our previous data showed that M. leprae (ML), unlike M. bovis BCG, did not induce an inflammatory response in the mice subcutaneou s tissue. Further, ML inhibited BCG-induced foot pad oedema and seemed to t ransform macrophages in epithelioid cells. Since these mycobacteria share c ommon antigens, here we seeked to compare the acute and chronic cellular re sponse evoked by ML and BCG in pleurisy of a mycobacteria-susceptible mice (BALB/c). The total leukocytes, the cell type that migrated to the pleural cavity and macrophage activation assayed by nitric oxide release were deter mined. Live or dead BCG Moreau recruited the same extent of cells, essentia lly monocytes and neutrophils, dose-dependently, in both acute and chronic pleurisy. BCG-induced eosinophilia was observed only in the acute response (after 24 h of injection). A significant nitric oxide release by pleural ma crophages was triggered by BCG Moreau without previous activation. Neverthe less, ML failed to recruit leukocytes to the pleural space or to lead to ni tric oxide production despite the number of bacilli used and the time studi ed (1, 7 or 14 days after injection). Although these mycobacteria have comm on antigens that cross-react, these data show a distinct ability of ML or B CG to recruit cells to the pleural space and to activate pleural macrophage for nitric oxide production in vivo.