RESUMO
Recent studies demonstrated the crucial role of c-Rel in directing Treg lineage commitment and its involvement in T helper 1 (Th1) cell-mediated autoimmune inflammation. We thus wondered whether these opposite functions of c-Rel influence the course of antiparasitic immune responses against Leishmania major, an accepted model for the impact of T-cell subsets on disease outcome. Here we show that c-Rel-deficient (rel(-/-) ) mice infected with L. major displayed dramatically exacerbated leishmaniasis and enhanced parasite burdens. In contrast to WT mice, IFN-γ and IL-17 production in response to L. major antigens was severely impaired in rel(-/-) mice. Reconstitution of Rag1(-/-) T-cell deficient mice with rel(-/-) CD4(+) T cells followed by L. major infection demonstrated that c-Rel-deficient T cells mount normal Th1 responses and are able to contain the infection. Similarly, Th1 differentiation of naïve CD4(+) cells in vitro was normal. Notably, a selective defect in IL-12 and IL-23 production was observed in rel(-/-) DCs compared with their WT counterparts. In conclusion, our data suggest that the expression of c-Rel in myeloid cells is essential for clearance of L. major and that this c-Rel-mediated effect is dominant over the lack of Tregs.
Assuntos
Leishmania major/imunologia , Leishmaniose Cutânea/imunologia , Proteínas Proto-Oncogênicas c-rel/metabolismo , Células Th1/imunologia , Células Th17/imunologia , Animais , Diferenciação Celular , Proteínas de Homeodomínio/genética , Interferon gama/biossíntese , Interleucina-12/deficiência , Interleucina-12/genética , Interleucina-17/biossíntese , Interleucina-23/genética , Leishmania major/fisiologia , Leishmaniose Cutânea/parasitologia , Macrófagos/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Proto-Oncogênicas c-rel/deficiência , Proteínas Proto-Oncogênicas c-rel/genética , Linfócitos T Reguladores/imunologiaRESUMO
The early growth response gene product Egr-1 has been shown to have great impact on growth, proliferation, and differentiation in a wide variety of cells, including T cells. In this study, we show that Egr-1 is rapidly induced upon T cell stimulation and is expressed predominantly in T helper type 2 (Th2) compared with type 1 (Th1) cells. We further investigate the role of Egr-1 in regulation of the Th2 cytokine interleukin-4 (IL-4) expression. IL-4 is a key Th2 cytokine that regulates humoral immunity and also causes allergic inflammation. Regulation of IL-4 gene transcription in Th2 cells has been shown to be controlled by multiple T cell receptor (TCR)-induced transcription factors. However, only a few transcription factors were shown to be selectively induced in differentiated Th2 cells in response to TCR stimulation. Chromatin immunoprecipitation analysis demonstrates that Egr-1 binds to the IL-4 promoter in vivo upon T cell stimulation. Ectopic expression of Egr-1 enhances endogenous IL-4 mRNA expression and elevates IL-4 promoter activity. We also show that Egr-1, nuclear factor of activated T cell, and NF-kappaB cooperatively bind to an NFAT/NF-kappaB-overlapping IL-4 enhancer element and activate the IL-4 promoter synergistically. Furthermore, we show that antisense oligonucleotides that knock down Egr-1 expression attenuate IL-4 transcription. Our study provides the first evidence that Egr-1 protein is differentially expressed in Th1 and Th2 cells and is involved in the acute phase of the IL-4 transcription in response to TCR stimulation.
Assuntos
Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Regulação da Expressão Gênica , Interleucina-4/genética , Células Th1/metabolismo , Células Th2/metabolismo , Transcrição Gênica , Animais , Sítios de Ligação , Diferenciação Celular , Linhagem Celular , Regulação para Baixo , Proteína 1 de Resposta de Crescimento Precoce/genética , Elementos Facilitadores Genéticos/genética , Humanos , Camundongos , NF-kappa B/metabolismo , Fatores de Transcrição NFATC/metabolismo , Oligonucleotídeos Antissenso/genética , Oligonucleotídeos Antissenso/metabolismo , Regiões Promotoras Genéticas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Células Th1/citologia , Células Th2/citologia , Fatores de TempoRESUMO
Transcription factors of the interferon regulatory factor (IRF) family contribute to the regulation of cell proliferation and apoptosis. Here, we show that CD4(+) T helper (Th) cells lacking IRF4 (IRF4(-/-)) are highly sensitive to apoptosis. After infection of IRF4(-/-) mice with the protozoan parasite Leishmania major, the lesion-draining lymph nodes developed the prototypic lymphadenopathy of wild-type mice after 4 wk, but demonstrated almost total loss of cellularity and enhanced apoptosis after 7 wk. In vitro, activation of IRF4(-/-) CD4(+) Th cells led to greatly increased apoptosis compared with wild-type cells. Coculture of IRF4(-/-) and IRF4(+/+) CD4(+) cells did not increase survival of IRF4(-/-) CD4(+) cells, indicating that the enhanced rate of IRF4(-/-) Th cell apoptosis was neither transferable nor due to lack of a cytokine. Enhanced CD4(+) cell apoptosis was also observed after anti-CD95 mAb treatment, despite normal CD95 expression. Removal of endogenous cytokines, notably interleukin (IL)-4, led to increased and equally high levels of IRF4(-/-) and IRF4(+/+) cell apoptosis, whereas the protective activity of exogenous IL-4 was reduced in IRF4(-/-) CD4(+) cells despite normal expression of the IL-4 receptor. Therefore, IRF4 is central in protecting CD4(+) cells against proapoptotic stimuli.
