Antigen specificity shapes antibody functions in tuberculosis.

Tuberculosis (TB) is the number one infectious disease cause of death worldwide due to an incomplete understanding of immunity. Emerging data highlight antibody functions mediated by the Fc domain as immune correlates. However, the mechanisms by which antibody functions impact the causative agent Mycobacterium tuberculosis (Mtb) are unclear. Here, we examine how antigen specificity determined by the Fab domain shapes Fc effector functions against Mtb. Using the critical structural and secreted virulence proteins Mtb cell wall and ESAT-6 & CFP-10, we observe that antigen specificity alters subclass, antibody post-translational glycosylation, and Fc effector functions in TB patients. Moreover, Mtb cell wall IgG3 enhances disease through opsonophagocytosis of extracellular Mtb. In contrast, polyclonal and a human monoclonal IgG1 we generated targeting ESAT-6 & CFP-10 inhibit intracellular Mtb. These data show that antibodies have multiple roles in TB and antigen specificity is a critical determinant of the protective and pathogenic capacity.