Increased capillary permeability mediated by a dengue virus-induced lymphokine

The mechanism of increased capillary permeability, seen in cases of dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS), is not known. Dengue type 2 virus (DV) is known to induce production of a lymphokine, the cytotoxic factor (CF), by the T lymphocytes of mouse spleen. The data presented here show that intraperitoneal inoculation of CF in mice results in increased capillary permeability in a dose-dependent manner, as shown by leakage of intravenously injected radiolabelled iodine (125I) or Evans blue dye. Peak leakage occurred 30 min after inoculation of CF and the vascular integrity was restored by 2 hr. The increase in capillary permeability was abrogated by pretreatment of mice with anti-CF antibodies, avil (H1 receptor blocker) or ranitidine (H2 receptor blocker). The findings thus show that a DV-induced lymphokine, the CF, increases the capillary permeability via release of histamine.