Antibodies are well known for their role in protecting individuals against infection, however in certain cases the production of specific antibody can actually promote disease. Antibody-dependent enhancement (ADE) of infection is well described for viral disease; however, antibodies that enhance bacterial disease are relatively unknown. Pseudomonas aeruginosa is a bacterial pathogen that is increasingly resistant to last resort antibiotics and new treatments are desperately needed. We previously identified patients that produced a specific antibody that protected their infecting P. aeruginosa from killing by the immune system. These ‘cloaking antibodies’ target lipopolysaccharide on the bacterial surface. Importantly, patients with these antibodies have worse lung function and outcomes that patients with normal complement-killing. Here I’ll discuss my recent research into the clincal impact of cloaking antibodies in P. aeruginosa bloodstream infections and in people with cystic fibrosis. Recent evidence of a novel mechanism linking these antibodies to inflammation will also be shown.