Depressed macrophage functions in dengue virus-infected mice: role of the cytotoxic factor

Dengue virus Type 2 (DV) infection causes immunosuppression in mice. Since macrophages are crucial for immune response, we have studied their functions in this condition and report our findings here. It was observed that in DV-infected mice the phagocytosis of neutral-red and latex particles by splenic and peritoneal-cavity macrophages was significantly reduced (P less than 0.001) from Days 3 to 10 after inoculation. Similarly the migration of splenic and peritoneal macrophages on a glass surface was reduced significantly (P less than 0.001) from Days 4 to 10 after inoculation. Pre-treatment of normal mouse spleen cells with DV-induced cytotoxic factor (CF) inhibited the phagocytic and migratory functions in the same way as observed in DV-infected mice. Higher dilutions of CF (10(-3) and 10(-3.7)) did not kill the cells but affected their functions. It was concluded that macrophage functions are affected by killing and metabolic changes in these cells by DV-induced CF, thus producing immunosuppression.