The infiltration of neutrophils which phagocytose and kill microorganisms is an important defense mechanism against infections of the airways. Bordetella pertussis is a human respiratory pathogen which colonizes ciliated epithelium, causing whooping cough. We have investigated the effects of the peptidoglycan fragment tracheal cytotoxin (TCT) of B. pertussis on human neutrophil function in vitro. TCT (10(-6) to 10(-8) M) was toxic for human neutrophils, as measured by lactate dehydrogenase release and levels of intracellular ATP. TCT (10(-9) to 10(-15) M) did not stimulate neutrophil migration or chemiluminescence and did not affect neutrophil phagocytosis. Incubation of neutrophils for 20 min with TCT (10(-9) to 10(-11) M) significantly inhibited (P < 0.05) their subsequent migration toward the chemotactic factor N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP; 10(-9) M). Incubation of neutrophils for 20 min with TCT (10(-9) to 10(-15) M) significantly inhibited (P < 0.05) chemiluminescence stimulated by FMLP (10(-5) M). TCT (10(-6) to 10(-12) M) did not stimulate interleukin-1 alpha production by neutrophils or serum complement activation by the alternate pathway. We conclude that TCT at concentrations of < 10(-8) M affects important neutrophil functions and at higher concentrations is toxic. TCT may therefore contribute to the survival of B. pertussis within the airways in vivo.