Specific binding of human alpha interferon to high-affinity cell-surface binding sites on peripheral blood mononuclear cells.
To characterize receptors for alpha interferon (IFN-alpha) on human cells, we studied the binding of radioiodinated recombinant DNA-derived human IFN-alpha to human peripheral blood mononuclear cells (PBMCs) from normal individuals and from patients with chronic type B hepatitis. At 1 degree C, binding reached equilibrium after 2 to 3 hours of incubation, and saturation of specific binding occurred at a concentration of approximately 4000 fmol/ml. Binding of labeled IFN-alpha was specific; it was inhibited by an excess of unlabeled IFN-alpha or IFN-beta but not by cholera toxin or IFN-gamma. Scatchard analysis of binding data yielded for normal PBMCs an apparent dissociation constant (Kd) of 1.54 +/- 0.49 x 10(-9) mol/L (mean +/- SD) and an apparent maximum binding capacity (Bmax) of 7.35 +/- 1.22 x 10(-11) mol/L. Corresponding values for patients with chronic type B hepatitis who had not received treatment were similar, suggesting that such patients should respond normally to endogenous interferon. Analysis of data on the binding of labeled IFN-alpha to normal PBMCs from experiments in which a high specific activity ligand or subpopulations of PBMCs had been used revealed that receptors for IFN-alpha on PBMCs are heterogenous. In patients with chronic type B hepatitis who were receiving IFN-alpha therapy, the apparent Kd was increased (3.02 +/- 0.91 x 10(-9) mol/L) without any appreciable change in the apparent Bmax or any appreciable changes in the proportions of subpopulations of PBMCs. This decreased affinity induced by IFN-alpha treatment does not necessarily reflect an effect on a single binding site.(ABSTRACT TRUNCATED AT 250 WORDS)
Dooley
J S
JS
Liver Diseases Section, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892.
Vergalla
J
J
Hoofnagle
J H
JH
Zoon
K C
KC
Munson
P J
PJ
Jones
E A
EA
D001665:Binding Sites; D001667:Binding, Competitive; D006801:Humans; D066298:In Vitro Techniques; D007370:Interferon Type I / Q000378:metabolism* / Q000627:therapeutic use; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism; D011971:Receptors, Immunologic / Q000032:analysis; D017471:Receptors, Interferon
D007370:Interferon Type I; D011971:Receptors, Immunologic; D017471:Receptors, Interferon