Antibodies have demonstrated having a protective effect in animal models of tuberculosis (TB). These experiments have considered the specificity of antigen recognition, and the different isotypes and subclasses, as significant contributors of this effect. However, the carbohydrate chain heterogeneity on the Fc region of IgG (Fc-IgG) can play an important role in modulating the immune response. TB patients usually have high titers of specific IgG, however the carbohydrate associated to Fc-IgG usually lacks galactose. To assess the effect of this abnormal IgG in murine pulmonary TB, we evaluated the specificity of recognition to M. tuberculosis antigens in vitro and protective effects in vivo comparing human intravenous immunoglobulin (IVIg) and IVIg treated with an endoglycosidase to remove the glycan residues (EndoS-treated IVIg). Our results showed similar antigen recognition. The study of distribution and kinetics of IVIg in serum and bronchial lavage after intraperitoneal (i.p.) administration in mice showed showed that IVIg circulates for 21 days. Finally, the protective effect of intact and EndoS-treated IVIg administered by i.p was studied in a murine model of progressive TB. IVIg treatment caused reduction of pulmonary bacilli loads, larger granulomas and less pneumonia, while animals treated with EndoS-treated IVIg were not protected compared to control animals. Thus, IVIg has a protective activity in experimental pulmonary TB and this effect requires intact Fc oligosaccharides. This article is protected by copyright. All rights reserved.