PT (Pertussis toxin) is a protein-based AB5-type exotoxin produced by the bacterium Bordetella pertussis, which causes whooping cough. Pertussis toxin is involved in the colonization of the respiratory tract and the establishment of infection. Research suggests pertussis toxin may have a therapeutic role in treating a number of common human ailments, including hypertension, viral infection, and autoimmunity.