High-affinity receptors for human interferon in bovine lung and human placenta

Membrane fractions were prepared from fresh frozen bovine lung tissue and human placenta and used for receptor binding studies with recombinant DNA produced human-alpha-interferon (IFN-alpha). A single class of high-affinity binding sites was determined for bovine lung (Ka = 1.5 X 10(10) M) and human placenta (Ka = 3.7 X 10(9) 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-alpha 2 to cultured Daudi cells (Ka = 2.5 X 10(10) 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.