Characterization of the Binding of Radioiodinated Hybrid Recombinant IFN-αA/D to Murine and Human Lymphoid Cell Lines

Abstract

The hybrid recombinant human interferon (IFN) rIFN-αA/D was radioiodinated. Specific binding of [¹²⁵I]rIFN-αA/D was observed with both human and murine cell lines. The binding of [¹²⁵I]rIFN-αA/D to human Daudi cells had similar characteristics to the previously described binding of [¹²⁵I]rIFN-αA or -α₂. The following lines of evidence demonstrated that [¹²⁵I]rIFN-αA/D bound with high affinity to the same receptor on murine cells as murine IFN-α and -β: (i) the binding of [¹²⁵I]rIFN-αA/D to murine LBRM cells was inhibited to a similar extent by natural murine IFN-α, natural murine IFN-β, and rIFN-A/D; (ii) the K _d (∼2 χ 10⁻¹⁰ M) obtained from both competition experiments and saturation binding experiments with [¹²⁵I]rIFN-αA/D was comparable to the previously reported K _d for the binding of natural murine IFN-α and -β to other murine cell lines; (iii) the size of the cross-linked [¹²⁵I]rIFN-αA/D receptor complex formed on murine LBRM cells was similar to the previously reported cross-linked complex formed after binding radioiodinated natural murine IFN-β to other murine cell lines. Due to the current lack of readily available recombinant murine IFN-α or -β for radiolabeling and the previously demonstrated biological activity of rIFN-αA/D on murine cells, [¹²⁵I]rIFN-αA/D should prove to be a useful reagent for further studies of murine IFN receptors.