Antibody neutralization studies of the antiviral activities of human leukocyte interferon on different cells.

Human leukocyte and fibroblast interferons were titrated by inhibition of a single cycle of virus replication on different cells which vary in sensitivities to the action of human interferons. The interferon dose response curves were found to be regularly sigmoidal, exhibit similar slopes, and reflect the relative sensitivities of each cell type to the antiviral activities of the human interferons. The degree and pattern of antibody neutralization for a constant quantity of leukocyte interferon was determined on the various cell types by virus yield assays. The antibody neutralization curves reveal the quantity of antibody required to neutralize the antiviral activity of the leukocyte interferon on each of the different cells. Because of the high degree of sensitivity of the assay system, the presence of very low levels of antigenically distinct interferons in the preparation can be detected.