SUMMARYBovine interferon-0ql (IFN-cti1) and porcine interferon-y (IFN-~) inhibited African swine fever virus replication in both porcine monocytes and alveolar macrophages. The most potent antiviral activity was observed with IFN-y-treated alveolar macrophages. The production of both a virulent (CC83) and a non-virulent (BA71) isolate of the virus was inhibited. Bovine turnout necrosis factor ~ did not show antiviral activity in either monocytes or alveolar macrophages. Rather, an increase of African swine fever virus production in tumour necrosis factor or-treated monocytes was found. An analysis of viral protein synthesis in IFN-~tI1-and IFN-~,-treated alveolar macrophages showed an inhibition of synthesis of some viral proteins. The inhibition of late proteins was very pronounced in IFN-~-treated cells, and it was probably a consequence of the inhibition of African swine fever virus DNA polymerase activity.

A method of loading macrophages from normal and inflammatory mouse peritoneal exudates with 59Fe using 59Fe, 125I-transferrin-antitransferrin immune complexes is described and the subsequent release of iron and degraded transferrin to the incubation medium has been studied. Release of iron occurred more rapidly from resident macrophages than from thioglycollate broth-induced (stimulated) macrophages, but degradation of the 125I-transferrin in the immune complexes was faster in stimulated cells. A small percentage of the iron released was in the form of ferritin. Desferrioxamine (1 mM) increased the release of iron from both stimulated and resident macrophages, the effect being proportionally greater in the stimulated cells. Ascorbic acid (1 mM) had no effect on the release of iron, nor did the addition of apotransferrin (1 mg/ml) to the culture medium. These results support the concept of a blockade of iron release by reticuloendothelial cells in states of inflammation, and suggest that it may be a primary cause of the anaemia of chronic disease.

Radioiodinated recombinant human interferon-gamma (IFN-y) bound to human monocytes, U937, and HL60 cells in a specific, saturable, and reversible manner. At 40C, the different cell types bound 3,000-7,000 molecules of IFNy, and binding was of comparable affinity (K. = 4-12 X 10 M-l). No change in the receptor was observed after monocytes differentiated to macrophages or when the cell lines were pharmacologically induced to differentiate. The functional relevance of the receptor was validated by the demonstration that receptor occupancy correlated with induction of Fc receptors on U937. Binding studies using U937 permeabilized with digitonin showed that only 46% of the total receptor pool was expressed at the cell surface. The receptor appears to be a protein, since treatment of U937 with trypsin or pronase reduced '251-IFNy binding by 87 and 95%, respectively. At 370C, ligand was internalized, since 32% of the cell-associated IFNy became resistant to trypsin stripping. Monocytes degraded '251-IFNy into trichloroacetic acid-soluble counts at 370C but not at 40C, at an approximate rate of 5,000 molecules/cell per h. The receptor was partially characterized by SDS-polyacrylamide gel electrophoresis analysis of purified U937 membranes that had been incubated with _251-IFNy. After cross-linking, the receptor-ligand complex migrated as a broad band that displayed an M, of 104,000±18,000 at the top and 84,000±6,000 at the bottom. These results thereby define and partially characterize the IFNy receptor of human mononuclear phagocytes.