Differential regulation of gene expression during macrophage activation with a polyribonucleotide. The role of endogenously derived IFN.

The activation of macrophages by exposure to the polyribonucleotide, poly I:C, is accompanied by a large stimulation of the synthesis of the C components factor B and C3, and a concomitant inhibition of the synthesis of the lysosomal enzyme beta-glucuronidase. Northern blot analysis of poly A+ RNA extracted from poly I:C-stimulated cells revealed that the changes in the synthesis of factor B and C3 were related to changes in the levels of their respective mRNA and hence the expression of these proteins appeared to be regulated at a pre-translational level. The down-regulation of the synthesis of beta-glucuronidase appeared to be regulated at both translational and pre-translational levels. In view of the proposed role of macrophage-derived IFN in the regulation of macrophage activation, we investigated the possible role of IFN-alpha/beta in the regulation of the synthesis of factor B, C3, and beta-glucuronidase. Exposure of macrophages to mouse IFN-alpha and IFN-beta induced limited changes in the synthesis of factor B, C3, and beta-glucuronidase. However, pretreatment of macrophages with only 500 U/ml of IFN-beta primed the cells thereby increasing their sensitivity to poly I:C. IFN-alpha was less effective as a priming agent. When macrophages were exposed to poly I:C in the presence of an anti-mouse IFN-alpha/beta antiserum, the changes in the synthesis of factor B, C3, and beta-glucuronidase were partially inhibited. Collectively, these data indicate first, that exposure of mouse bone marrow-derived macrophages to poly I:C differentially regulates the expression of the products of the genes for factor B, C3, and beta-glucuronidase. Second, IFN-alpha and IFN-beta prime macrophages to increase the sensitivity of macrophages to poly I:C. Third, in the absence of exogenous IFN, macrophage-derived IFN appears to participate in priming the cells in an autocrine or paracrine fashion.