title: Agonist and antagonist effects of interferon alpha and beta on activation of human macrophages. Two classes of interferon gamma receptors and blockade of the high-affinity sites by interferon alpha or beta.
abstract: H2O2-releasing capacity and limited antitoxoplasma activity could be induced in human macrophages (derived from monocytes cultured greater than or equal to 5 d) but not in monocytes themselves (cells cultured less than or equal to 4 d) by a further 3-d incubation with pure natural or rIFN-alpha or -beta. More than 3 pM (10 U/ml) of these IFNs was required, with greatest effects at approximately 300 pM (10(3) U/ml). At 300 pM, H2O2-releasing capacity was enhanced 4.4 +/- 1.6-fold over medium control (mean +/- SD for natural INF-alpha, rIFN-alpha A, rIFN-alpha D, and rIFN-beta) compared to an 8.4 +/- 4.8-fold increase with rIFN-gamma (100 pM, 100 U/ml) in the same experiments. Unexpectedly, low concentrations of IFN-alpha or -beta (3 fM-300 pM) blocked induction of H2O2-releasing capacity by rIFN-gamma (10 pM), with a 50% inhibitory dose of approximately 80 fM. However, IFN-alpha or -beta (3 fM-300 pM) could not inhibit the effect of higher concentrations of rIFN-gamma (1 nM). In contrast to results with monocytes or young macrophages, Scatchard plots of binding of 125I-rIFN-gamma to mature macrophages (day 8 of culture) indicated two classes of binding sites: approximately 2,000 high-affinity sites (Kd approximately 0.43 nM) and approximately 23,000 low-affinity sites (Kd approximately 6.4 nM) per cell. Binding of 125I-rIFN-gamma to the high- but not the low-affinity sites was blocked by simultaneously added IFN-alpha or -beta, with a 50% inhibitory dose of approximately 2 U/0.25 ml (approximately 2 pM), or reversed by subsequently added IFN-alpha or -beta. Thus, differentiation of human mononuclear phagocytes in vitro is accompanied by the emergence of (a) an agonist response to submicromolar concentrations of IFN-alpha or -beta, (b) antagonism of the effect of picomolar IFN-gamma by femtomolar IFN-alpha or -beta, (c) two classes of IFN-gamma-Rs, and (d) nonstimulatory binding of IFN-alpha or -beta to the high- but not the low-affinity IFN-gamma-Rs, with higher affinity than rIFN-gamma itself. We speculate that traces of IFN-alpha or -beta derived from stromal cells, parenchymal cells, or resident macrophages may dampen the activation of mature tissue macrophages by the small amounts of IFN-gamma that diffuse from inflammatory sites into normal tissues. Such a mechanism could constrain the potentially destructive phenomenon of macrophage activation to areas where monocytes have recently immigrated and/or the concentration of IFNs is high.
authors.affiliation: Beatrice and Samuel A. Seaver Laboratory, Department of Medicine, Cornell University Medical College, New York, New York 10021.
authors.forename: R
authors.initials: R
authors.lastname: Yoshida
authors.forename: H W
authors.initials: HW
authors.lastname: Murray
authors.forename: C F
authors.initials: CF
authors.lastname: Nathan
mesh_terms: D000328:Adult; D001667:Binding, Competitive; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007370:Interferon Type I / Q000494:pharmacology*; D007371:Interferon-gamma / Q000037:antagonists & inhibitors; D008262:Macrophage Activation / Q000187:drug effects*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010587:Phagocytosis / Q000187:drug effects; D011971:Receptors, Immunologic / Q000145:classification / Q000187:drug effects*; D017471:Receptors, Interferon; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D007370:Interferon Type I; D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D007371:Interferon-gamma; D006861:Hydrogen Peroxide