Studies on immunopathogenesis in epidemic hemorrhagic fever: sequential observations on activation of the first complement component in sera from patients with epidemic hemorrhagic fever.

Sequential measurements of activation of the 1st component of complement (C1) in the sera of 29 patients hospitalized with epidemic hemorrhagic fever (EHF) were performed according to a method recently developed. These patients were treated with supportive, routine therapy, but not immunosuppressive agents. This paper describes the kinetic observations on the activation of C1 in the 29 cases. The data confirm that an apparently increased extent of activation occurred in their sera. It was found that the more severely ill the patients were, the more apparent the activation. Additionally, beginning with the 15th day of disease, the extent of C1 activation diminished in most of the moderate and severe types of patients, but not in those with moribund illness and fatal ones. On the basis of the study, it may be reasonably concluded that C1 activation was correlated well with the severity and clinical course of EHF, indicating that the classical C pathway was activated in these patients. We feel that our findings are important to an understanding and elucidation of the immunopathogenetic mechanisms of EHF.