Variable Adjuvant Activity of Bordetella pertussis with Respect to the Primary and Secondary Immunization of Mice

We carried out a study on the adjuvant effect of Bordetella pertussis vaccine on the primary and secondary immune responses of the mouse to sheep erythrocytes, quantitating antibody-producing spleen cells and serum antibody. The simultaneous injection of sheep erythrocytes and B. pertussis, when compared to immunization with sheep red blood cells alone, resulted in an increased and prolonged multiplication of antibody-forming spleen cells. The adjuvant effect was also documented by increased production of serum hemolysins and agglutinins. Further, B. pertussis enhanced the priming effect of the antigen for the secondary response. However, when the bacterial adjuvant was given together with a second antigenic stimulus 41 days after the primary immunization, the peak values of direct and indirect plaque-forming spleen cells did not differ from the corresponding control animals further inoculated with sheep erythrocytes alone. Nonetheless, the influence of the bacterial adjuvant was still expressed by the delayed decrease of the numbers of plaque-forming spleen cells. On the basis of the X-Y-Z scheme it is suggested that B. pertussis cells as adjuvant enhance the multiplication of antigen-sensitive X cells or affect the initial stages of differentiation of these cells. This effect of the pertussis vaccine can be distinguished from a general proliferative action on other cells.