Argentine hemorrhagic fever. Alterations of the complement system and anti-Junin-virus humoral response.

We investigated immunologic mechanisms and the role of complement in the pathogenesis of Argentine hemorrhagic fever, a disease caused by the Junin virus, a member of the arenavirus group. Total serum complement activity was reduced to 68 per cent of control values in patients with severe or moderate disease (P less than 0.001). C2, C3 and C5 values were also low (12 to 60 per cent) during the early acute period of the disease. However, serum C4 content was increased to 160 per cent of the control values in the same patients. Total complement activity returned to normal with clinical and laboratory recovery, at the time of detection of antibodies against Junin virus. C1q reactive material was found in four of 19 cases and no relation to the evolution of the disease could be established. These results suggest that immune complexes are not important in the pathogenesis of Argentine hemorrhagic fever, but that activation of the complement system has a role.