Temporary appearance of a circulating granulocyte-macrophage colony-stimulating factor in lethal murine malaria.

Infection of mice with Plasmodium berghei engendered a temporary appearance of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the serum. The peak of GM-CSF levels was detected at day 2 post-infection, and then gradually decreased. On the other hand, the number of committed stem cells for granulocytes and macrophages (CFU-GM) in bone marrow transiently decreased at day 2 post-infection, and then increased and peaked at day 6 post-infection. When the serum of P. berghei-infected mice was fractionated by gel chromatography on Sephacryl S-300, GM-CSF activity was detected as a single peak with an apparent molecular weight of 64 KDa. GM-CSF was entirely adsorbed to concanavalin A-Sepharose 4B affinity chromatography, and was sensitive to pronase digestion, indicating its glycoprotein nature. These results suggest that the circulating GM-CSF would contribute the increase of granulocyte-macrophage hemopoiesis in the early phase of malaria.

Appearance of adherent cells suppressive to erythropoiesis during an early stage of Plasmodium berghei infection in mice.

We examined the effect of adherent cells from bone marrow or spleen of mice infected with Plasmodium berghei on dyserythropoiesis. Significant reduction in number of erythroid progenitors (erythroid colony-forming units: CFU-E and erythroid burst-forming units: BFU-E) was observed in bone marrow as early as 1 day after P. berghei infection. When adherent cells were removed from bone marrow or spleen cells of infected mice, the number of CFU-E and BFU-E was clearly increased. Furthermore, addition of adherent cells from infected mice to nonadherent cells from normal mice inhibited erythroid colony formation significantly in a dose-dependent manner. These results suggest that the adherent cells obtained from bone marrow or spleen of mice in the early stage of P. berghei-infection have a suppressive effect on erythropoiesis.