Fil: Romero, María M. Academia Nacional de Medicina. Instituto de Investigaciones Hematológicas Mariano R. Castex; Argentina.Fil: Basile, Juan I. Academia Nacional de Medicina. Instituto de Investigaciones Hematológicas Mariano R. Castex; Argentina.Fil: López, Beatriz. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Ritacco, Viviana. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Barrera, Lucía. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas; Argentina.Fil: Sasiain, María Del Carmen. Academia Nacional de Medicina. Instituto de Medicina Experimental; Argentina.Fil: Alemán, Mercedes. Academia Nacional de Medicina. Instituto de Investigaciones Hematológicas Mariano R. Castex; Argentina.Neutrophils (PMN) are the first cells to infiltrate the lung after infection, and they play a significant protective role in the elimination of pathogen, by releasing preformed oxidants and proteolytic enzymes from granules and generating ROS, thus limiting inflammation by succumbing to apoptosis. In a previous study, we found marked differences in ROS-induced apoptosis between two Mycobacterium tuberculosis (Mtb) strains, M and Ra, representative of widespread Mtb families in South America, i.e. Haarlem and Latin-American Mediterranean (LAM), being strain M able to generate further drug resistance and to disseminate aggressively.