RESUMO
Dendritic cell immunoreceptor (DCIR) deficiency is related to development of autoimmune disorders and DCIR gene polymorphisms are associated with rheumatoid arthritis (RA). We analyzed the mRNA expression from the four known transcripts of DCIR in IFN-gamma-treated human leukocytes together with fine mapping across the locus. RA patients and healthy controls were genotyped for several single nucleotide polymorphisms (SNPs) in DCIR and flanking regions. mRNA expression in peripheral blood mononuclear cells (PBMCs), stimulated with gamma-interferon (IFN-gamma) in vitro, was determined by transcript-specific PCR. Our data reveal that IFN-gamma significantly downregulates the average expression of transcripts DCIR_v1, DCIR_v2, DCIR_v3 and DCIR_v4 (P<0.0001 for v1, P<0.02 for v2, P<0.0001 for v3, P<0.001 for _v4, patients and controls, Wilcoxon signed-rank). The expression of DCIR showed significant association with variations in the gene. Cells with the RA-associated allele rs2024301 exhibit a significant increase in the expression of DCIR_v4. We also present a new fifth isoform lacking exons 2, 3 and 4. This data illustrate that common genetic variations may influence DCIR mRNA expression. We also show that the expression is regulated by the inflammatory mediator IFN-gamma, affecting all four transcripts and that this was independent of genotype.
Assuntos
Artrite Reumatoide/etiologia , Regulação da Expressão Gênica , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Isoformas de Proteínas/genética , Receptores Imunológicos/genética , Receptores Imunológicos/metabolismo , Fatores de Transcrição/metabolismo , Artrite Reumatoide/genética , Artrite Reumatoide/imunologia , Células Cultivadas , Regulação para Baixo , Feminino , Variação Genética , Humanos , Interferon gama/farmacologia , Lectinas Tipo C/efeitos dos fármacos , Masculino , Glicoproteínas de Membrana/efeitos dos fármacos , Isoformas de Proteínas/metabolismo , RNA Mensageiro/biossíntese , Receptores Imunológicos/efeitos dos fármacos , Padrões de Referência , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/genéticaRESUMO
OBJECTIVE: An association to variations in the dendritic cell immunoreceptor (DCIR) gene with rheumatoid arthritis (RA) was recently shown. However, protein expression of DCIR has so far not been assessed in a disease setting. In the present work, we aimed to determine the cellular and tissue distribution of this receptor in healthy controls and in patients with RA before and after local glucocorticoid administration. METHODS: DCIR mRNA expression was evaluated by quantitative PCR (n=3) and protein expression by flow cytometry (n=18), immunohistochemistry (n=14) and double immunofluorescence (n=5). RESULTS: DCIR protein was not detected in healthy synovia. By contrast, expression was abundant on cells from rheumatic joints in synovial fluid and in tissue. Following corticosteroid treatment this expression was downregulated. Interestingly, DCIR could be detected on natural killer (NK) cells and T cells, and CD4+ and CD8+, as well as on monocytes, B cells, dendritic cells and granulocytes. The frequency of DCIR+ T cells and the level of surface expression were increased in the rheumatic joint compared to blood. In synovial fluid the typical DCIR+ T cells were large activated cells, whereas blasted DCIR+ T cells were not detected in blood. CONCLUSIONS: We demonstrate increased protein and mRNA expression of DCIR in RA, especially in the rheumatic joint. Expression was widespread and included a subpopulation of T cells. This suggests that the inflammatory synovial environment induces DCIR expression, and this may be related to synovial T cell function. Ligation of DCIR, or lack thereof, could contribute to the chronic inflammation characterising autoimmune diseases such as RA.
