High-Affinity Receptors for Human Interferon in Bovine Lung and Human Placenta

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Abstract
Membrane fractions were prepared from fresh frozen bovine lung tissue and human placenta and used for receptor binding studies with recombinant DNA produced humanalpha-interferon (IFN-α). A single class of high-affinity binding sites was determined for bovine lung (Ka = 1.5 × 1010 M) and human placenta (Ka = 3.7 × 109 M) membranes, respectively. These values for the affinity of IFN binding are comparable within the range of observed error to that observed for the binding of human IFN-α2 to cultured Daudi cells (Ka = 2.5 × 1010 M). The type I IFN receptor content of bovine lung and human placenta membranes was 1.3 and 2.5 fmoles/mg wet weight, respectively. In addition, alterations in specific and nonspecific binding were observed with the bovine lung membrane incubations in the presence of calcium. Increases in specific binding of three- to fourfold were observed in the presence of 1 mM calcium chloride.