Pertussis, or whooping cough, is an extremely contagious bacterial respiratory infectious disease that prior to introduction of the DTP vaccine used to be the prime cause of infant mortality in wealthy countries. The bacterium produces a number of virulence factors and several protein toxins, of which the pertussis toxin (PT) and the adenylate cyclase toxin (ACT) employ differing mechanisms to manipulate the cAMP signaling pathways of host cells. In this talk I will focus on the less known AC toxin. I will describe how does it penetrate and hijack the sentinel cells of host immunity  and how does it paralyze the bactericidal functions of phagocytes.