We reported previously the isolation of a cDNA clone, designated NKG5, encoding a secreted protein that is expressed only in natural killer and T cells and is strongly upregulated upon cell activation. In this report we have isolated the NKG5 gene from a human placental genomic library and sequenced the gene and two kilobases of 5'-flanking DNA. Comparison with the cDNA sequence reveals that the NKG5 gene consists of five exons and four introns. Intron 1 contains a DNA segment that was reported to occur as an exon in 519, a closely related cDNA clone that was isolated from a T-cell library. This result indicates that NKG5 and 519 are alternative splicing products of a single gene. The 5'-flanking region of the NKG5 gene was analyzed for homology with the promoter regions of cytokines and other activation-induced genes showing lymphocyte-specific expression. Several segments displaying sequence similarity were identified. We also identified numerous sequence elements that have strong similarity to known binding sites for transcriptional regulatory proteins including T cell-specific and activation-specific regulatory factors. These findings are consistent with the cell-specific expression and the tight regulatory control that is observed for the NKG5 gene.

The ability of interleukin-1 (IL-1) to activate epidermal cell populations supports its role as a key cytokine in the pathogenesis of a number of inflammatory skin diseases. In the present study, we have examined the effect of interferon (IFN)-gamma on the expression of the IL-1 beta gene in mouse RAW 264.7 macrophages activated by lipopolysaccharide (LPS) plus tumor necrosis factor (TNF)-alpha. Incubation of macrophages with both LPS and TNF-alpha resulted in the expression of both IL-1 beta and inducible nitric oxide synthase (iNOS) mRNA transcripts and increased the release of IL-1 beta protein and nitrite production in culture supernatants. Addition of IFN-gamma up-regulated the expression of the iNOS gene in cells activated by LPS + TNF-alpha, but significantly suppressed the induction of IL-1 beta gene expression in a dose-dependent manner. The suppression required neither de novo protein synthesis nor involved destabilization of the mRNA transcripts. Together, these findings suggest that IFN-gamma can be an important regulatory cytokine in a chronic inflammatory site and may explain its purported anti-inflammatory effects in certain dermatological diseases.