Abstract
Binding of 125I-labelled human recombinant DNA interferons (IFNs) alpha-2, beta and gamma was compared on various human lymphoid cells and embryonic fibroblasts. While binding constants were within an order of magnitude for all three interferons (10-10 to 10-9 M), no competition was observed between IFN-γ on the one hand and IFN-α2 and IFN- on the other. However, consistent with previous reports, IFN-α2 and IFN- competed for presumably common receptors. Depending on the cell type, binding sites for IFN-γ were expressed in different numbers compared to those for IFN-α2 and IFN-. These direct comparative binding studies support the hypothesis that the receptor system for IFN-γ is unrelated to the IFN-α/ system.