Next generation of anti-anthrax vaccine must be based on well-defined component(s) eliciting easily assessed protective immune response. It is widely accepted that the anthrax protective antigen (PA) would be the key component of such a vaccine. At the same time, recent studies indicate that the immune response to the PA is complex, and additional research is needed to prepare safe and efficient PA-based vaccine prototype. In the present communication we discuss recently reported phenomenon of the antibody mediated enhancement of lethal toxin action.