PRODUCTION OF CYTOTOXIC FACTOR BY PERIPHERAL-BLOOD MONONUCLEAR-CELLS (PBMC) IN PATIENTS WITH DENGUE HEMORRHAGIC-FEVER

A unique cytokine, human cytotoxic factor (hCF), has been shown to occ ur in the sera of patients with dengue fever (DF) and dengue haemorrha gic fever (DHF). The present study was undertaken to investigate the a bility of fresh PBMC of such patients to produce hCF. The PBMC were cu ltured for 24 h and the culture supernatants (CS) were analysed for th e presence of hCF by cytotoxicity assay, competitive ELISA and dot blo t tests. In 90% of 246 cases CS were positive for hCF by the three tes ts. CS were positive for hCF in PBMC collected from days 1-20 of illne ss but not at later periods. Higher cytotoxic activity was observed in CS of days 1-4 of illness and was highest in cases of DHF grade IV an d lowest in cases of DF. Dot blot hybridization of RNA extracted from the PBMC of the patients showed the presence of mRNA for hCF in 94% of cases. A similar number of patients showed the presence of hCF in sit u in the PBMC smears by fluorescent antibody technique, hCF was found only in CD4(+) T cells. The findings thus present direct evidence of t he production of hCF by CD4 T cells of cases of DF/DHF.