Fig. 1.

A typical dot blot test for detection of human cytotoxic factor (hCF) in the culture supernatants (CS) of PBMC of the cases of various grades of dengue illness and normal healthy controls. Cultures were prepared (1 × 10⁶ cells/ml) in 4-cm Nunc Petri dishes and incubated at 37°C in the presence of 5% CO₂ and harvested after 24 h. CS were blotted on nitrocellulose membrane and were blocked. Blots were treated with anti-hCF antibody followed by anti-mouse IgG + horseradish peroxidase and then developed with substrate diaminobenzidine as described in Patients and Methods. The controls included CS from normal healthy individuals' PBMC (lane 9, A–H; lane 11, F–H); and purified hCF (1 μg/ml and its doubling dilutions) as positive control (lane 10, A–D).