RESUMO
Dendritic cells (DC) comprise a key part of the innate immune system that, upon activation, profoundly influences the nature of the adaptive T cell response. In this study, we present evidence that signaling lymphocytic activation molecule (SLAM), a molecule first identified in activated T and B cells, is strongly up-regulated in DC activated through CD40, as well as in response to inflammatory stimuli, including polyinosinic polycytidylic acid and LPS. mRNA encoding both membrane-bound and soluble secreted isoforms of SLAM was detected in CD40 ligand-activated DC, comprising two of the four known SLAM isoforms. Expression of membrane-bound SLAM protein peaked at 12 h poststimulation with CD40 ligand, gradually returning to baseline levels after 6 days. SLAM up-regulation appears to be a direct result of the induction of DC maturation, as inflammatory cytokines released during this process do not affect SLAM expression. Functionally, engagement of SLAM enhances DC production of IL-12 and IL-8, while having no effect on production of IL-10. Because SLAM is involved in the activation of T cells, the expression of SLAM on DC may provide a bidirectional signaling mechanism in which interacting DC and T cells are simultaneously and synergistically activated to mount proinflammatory Th1 responses.
Assuntos
Ligante de CD40/fisiologia , Células Dendríticas/metabolismo , Glicoproteínas/biossíntese , Imunoglobulinas/biossíntese , Mediadores da Inflamação/metabolismo , Ativação Linfocitária/fisiologia , Isoformas de Proteínas/biossíntese , Células Th1/metabolismo , Adulto , Antígenos CD , Apoptose/genética , Divisão Celular/genética , Quimiocinas/biossíntese , Quimiocinas/genética , Citocinas/biossíntese , Citocinas/genética , Proteínas do Citoesqueleto/biossíntese , Proteínas do Citoesqueleto/genética , Células Dendríticas/efeitos dos fármacos , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Glicoproteínas/genética , Humanos , Imunoglobulinas/genética , Lipopolissacarídeos/farmacologia , Poli I-C/farmacologia , Isoformas de Proteínas/genética , RNA Mensageiro/biossíntese , Receptores de Superfície Celular , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Membro 1 da Família de Moléculas de Sinalização da Ativação Linfocitária , Técnica de Subtração , Transcrição Gênica/efeitos dos fármacosRESUMO
The interaction of CD40 ligand (CD40L) expressed by activated T cells with CD40 on macrophages has been shown to be a potent stimulus for the production of IL-12, an obligate signal for generation of Th1 cytokine responses. The expression and interaction of CD40 and CD40L were investigated in human infectious disease using leprosy as a model. CD40 and CD40L mRNA and surface protein expression were predominant in skin lesions of resistant tuberculoid patients compared with the highly susceptible lepromatous group. IL-12 release from PBMC of tuberculoid patients stimulated with Mycobacterium leprae was partially inhibited by mAbs to CD40 or CD40L, correlating with Ag-induced up-regulation of CD40L on T cells. Cognate recognition of M. leprae Ag by a T cell clone derived from a tuberculoid lesion in the context of monocyte APC resulted in CD40L-CD40-dependent production of IL-12. In contrast, M. leprae-induced IL-12 production by PBMC from lepromatous patients was not dependent on CD40L-CD40 ligation, nor was CD40L up-regulated by M. leprae. Furthermore, IL-10, a cytokine predominant in lepromatous lesions, blocked the IFN-gamma up-regulation of CD40 on monocytes. These data suggest that T cell activation in situ by M. leprae in tuberculoid leprosy leads to local up-regulation of CD40L, which stimulates CD40-dependent induction of IL-12 in monocytes. The CD40-CD40L interaction, which is not evident in lepromatous leprosy, probably participates in the cell-mediated immune response to microbial pathogens.
Assuntos
Antígenos CD40/fisiologia , Citocinas/biossíntese , Hanseníase Virchowiana/imunologia , Hanseníase Tuberculoide/imunologia , Glicoproteínas de Membrana/fisiologia , Células Th1/imunologia , Células Th1/metabolismo , Antígenos CD40/biossíntese , Antígenos CD40/genética , Antígenos CD40/metabolismo , Ligante de CD40 , Membrana Celular/genética , Membrana Celular/imunologia , Membrana Celular/metabolismo , Células Cultivadas , Humanos , Imunidade Celular , Interleucina-12/biossíntese , Hanseníase Virchowiana/metabolismo , Hanseníase Virchowiana/patologia , Hanseníase Tuberculoide/metabolismo , Hanseníase Tuberculoide/patologia , Ligantes , Glicoproteínas de Membrana/biossíntese , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Monócitos/imunologia , Monócitos/metabolismo , Mycobacterium leprae/imunologia , RNA Mensageiro/biossíntese , Regulação para Cima/genética , Regulação para Cima/imunologiaRESUMO
The generation of cell-mediated immunity against many infectious pathogens involves the production of interleukin-12 (IL-12), a key signal of the innate immune system. Yet, for many pathogens, the molecules that induce IL-12 production by macrophages and the mechanisms by which they do so remain undefined. Here it is shown that microbial lipoproteins are potent stimulators of IL-12 production by human macrophages, and that induction is mediated by Toll-like receptors (TLRs). Several lipoproteins stimulated TLR-dependent transcription of inducible nitric oxide synthase and the production of nitric oxide, a powerful microbicidal pathway. Activation of TLRs by microbial lipoproteins may initiate innate defense mechanisms against infectious pathogens.
