Measurement of Interferon from in vitro Stimulated Lymphocytes by Bioassay and Monoclonal Antibody-based Immunoassay

1 MRC Division of Communicable Diseases, Clinical Research Centre, Watford Road, Harrow, Middlesex, HA1 3UJ, U.K. 2 MRC Laboratory for Molecular Biology, Hills Road, Cambridge CB2 2QQ and 3 Boots-Celltech Diagnostics Ltd., 240 Bath Road, Slough, Berkshire, SL1 4ET, U.K. Peripheral blood mononuclear cells (PBMC) derived from healthy individuals were stimulated with u.v.-inactivated Newcastle disease virus and the cell supernatants were assayed for both antiviral activity and alpha interferon (IFN- ) immunoreactivity. IFN- concentrations determined by two immunoradiometric assays (IRMAs) based on monoclonal antibodies that recognize different IFN- subtypes correlated well together ( r = 0.96) and with interferon concentrations determined by the two bioassays ( r = 0.82 to 0.89), but the agreement between the results of the two bioassays was not as close ( r = 0.79). As judged by the agreement between determinations on duplicate inductions of the same PBMC, the IRMAs were considerably more precise than the bioassays. Despite the use of a common IFN standard there were marked differences in the absolute titres of IFN determined by the IRMAs and bioassays, highlighting the difficultires in standardizing assays for IFN- . The IRMA results suggest that there are no major differences in the spectrum of IFN- subtypes produced by healthy individuals under conditions of viral stimulation. Keywords: IFN- , immunoradiometric assays, monoclonal antibodies Present address: Department of Clinical Microbiology, University College Hospital, Grafton Way, London WC1E 6AU, U.K. Present address: G. D. Searle & Co. Ltd., Lane End Road, High Wycombe, Bucks., HP12 4HL. U.K. Received 2 November 1984; accepted 20 March 1985.