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.
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.
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R Yoshida, H W Murray, C F Nathan; 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.. J Exp Med 1 March 1988; 167 (3): 1171–1185. doi: https://doi.org/10.1084/jem.167.3.1171
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