Abstract

The ability of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) to activate human monocytes/macrophages for virulent Paracoccidioides brasiliensis killing was evaluated. Peripheral blood monocytes (MO) and monocyte-derived macrophages (M∅) were activated with different concentrations of GM-CSF. Afterwards, cells were challenged with P. brasiliensis strain 18 (Pb18) and the fungicidal activity was evaluated, plating and counting the Colony Forming Units (CFU) after 10 days. GM-CSF activated MO and M∅ for P. brasiliensis killling in a concentration-dependent manner. There was an association between this fungicidal activity and the high levels of H₂O₂ release by the activated cells. Moreover, the killing effect was inhibited by Catalase (CAT), confirming the role of H₂O₂ in this process. On the other hand, L-Monomethyl-Arginine (L-NMMA) had no effect on fungicidal activity, showing that nitric oxide (NO) is not involved in killing by human cells against P. brasiliensis. Based on these data, the role of GM-CSFactivated human cells in the innate defense mechanisms against P. brasiliensis is discussed.

Keywords: Paracoccidioidomycosis; Paracoccidioides brasiliensis; Human monocytes; Human macrophages; GM-CSF; Fungicidal activity; H₂O₂; NO; ROS