Activation of liver macrophages in murine malaria is enhanced by vaccination

During blood-stage infection of mice with a lethal variant of Plasmodium yoelii, cells in both spleen and liver became activated to reach a peak at day 5. In mice protected by vaccination, activation was accelerated after infection. The most striking difference observed was in the 10-fold greater yield of infiltrating cells, including macrophages, obtained from the liver just before the mice recovered. Their capacity to give an oxidative burst and their cytotoxic activity against tumour cells was also more than 10 times normal. This suggests that the recruitment of inflammatory cells to the liver plays an important role in the protection of vaccinated mice against malaria.