Immune responses to Bordetella pertussis infection and vaccination

To assess antibody and cellular immune responses, 156 healthy children were immunized at approximately 18 months of age with acellular diphtheria-tetanus-pertussis vaccine. Changes in antibody responses to filamentous hemagglutinin (FHA) and to pertussis toxin (PT) were similar in pattern, and antibody titers reached values equal to those from patients with convalescent-stage pertussis. The FHA-induced DNA synthesis in peripheral blood mononuclear cells was maximum at 4 weeks after the primary series, and these levels were equal to those of patients with pertussis. High amounts of PT-induced DNA synthesis were observed in both immunized and nonimmunized children; thus, PT seemed to act mainly as a nonspecific mitogen. Almost the same responses to several mitogens that activate different subsets of lymphocytes were observed in young infants compared with older children. Furthermore, young infants who had Bordetella pertussis infection responded by FHA stimulation almost as well as older children.