Failure of malaria vaccination in mice born to immune mothers. II. Induction of specific suppressor cells by maternal IgG.

Female BALB/c mice were vaccinated against blood stage P. yoelii malaria, infected 2 weeks later and after recovery mated to C57B1/6 males. When their offspring were subsequently vaccinated, the effectiveness of vaccination, as assessed by survival after infection, was significantly impaired until 8 weeks of age. Cell and serum transfer experiments indicated that specific maternally derived IgG interferes with protection in two distinct ways: (1) directly by prevention of priming by the vaccine and (2) indirectly by the induction and maintenance of specific suppressor T cells (TS) which act to inhibit the generation of memory T helper cells involved in IgG production, as measured by the response to TNP-P. yoelii. Furthermore, it is shown that the maternal IgG and the TS cells act in synergy to abolish the protective effect of vaccination.