RESUMO
Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening hyperferritinemic systemic inflammatory disorders. Although profound cytotoxic impairment causes familial HLH (fHLH), the mechanisms driving non-fHLH and MAS are largely unknown. MAS occurs in patients with suspected rheumatic disease, but the mechanistic basis for its distinction is unclear. Recently, a syndrome of recurrent MAS with infantile enterocolitis caused by NLRC4 inflammasome hyperactivity highlighted the potential importance of interleukin-18 (IL-18). We tested this association in hyperferritinemic and autoinflammatory patients and found a dramatic correlation of MAS risk with chronic (sometimes lifelong) elevation of mature IL-18, particularly with IL-18 unbound by IL-18 binding protein, or free IL-18. In a mouse engineered to carry a disease-causing germ line NLRC4T337S mutation, we observed inflammasome-dependent, chronic IL-18 elevation. Surprisingly, this NLRC4T337S-induced systemic IL-18 elevation derived entirely from intestinal epithelia. NLRC4T337S intestines were histologically normal but showed increased epithelial turnover and upregulation of interferon-γ-induced genes. Assessing cellular and tissue expression, classical inflammasome components such as Il1b, Nlrp3, and Mefv predominated in neutrophils, whereas Nlrc4 and Il18 were distinctly epithelial. Demonstrating the importance of free IL-18, Il18 transgenic mice exhibited free IL-18 elevation and more severe experimental MAS. NLRC4T337S mice, whose free IL-18 levels were normal, did not. Thus, we describe a unique connection between MAS risk and chronic IL-18, identify epithelial inflammasome hyperactivity as a potential source, and demonstrate the pathogenicity of free IL-18. These data suggest an IL-18-driven pathway, complementary to the cytotoxic impairment of fHLH, with potential as a distinguishing biomarker and therapeutic target in MAS.
Assuntos
Interleucina-18/imunologia , Síndrome de Ativação Macrofágica/imunologia , Transdução de Sinais/imunologia , Substituição de Aminoácidos , Animais , Proteínas Reguladoras de Apoptose/genética , Proteínas Reguladoras de Apoptose/imunologia , Proteínas Adaptadoras de Sinalização CARD/genética , Proteínas Adaptadoras de Sinalização CARD/imunologia , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/imunologia , Humanos , Inflamassomos/genética , Inflamassomos/imunologia , Peptídeos e Proteínas de Sinalização Intercelular/genética , Peptídeos e Proteínas de Sinalização Intercelular/imunologia , Interleucina-18/genética , Interleucina-1beta/genética , Interleucina-1beta/imunologia , Mucosa Intestinal/imunologia , Mucosa Intestinal/patologia , Linfo-Histiocitose Hemofagocítica/genética , Linfo-Histiocitose Hemofagocítica/imunologia , Linfo-Histiocitose Hemofagocítica/patologia , Síndrome de Ativação Macrofágica/genética , Síndrome de Ativação Macrofágica/patologia , Camundongos , Camundongos Knockout , Mutação de Sentido Incorreto , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Proteína 3 que Contém Domínio de Pirina da Família NLR/imunologia , Pirina/genética , Pirina/imunologia , Transdução de Sinais/genéticaAssuntos
Anticorpos Monoclonais/uso terapêutico , Doenças Autoimunes/tratamento farmacológico , Linfócitos B/efeitos dos fármacos , Fatores Imunológicos/uso terapêutico , Anticorpos Monoclonais Murinos , Doenças Autoimunes/imunologia , Linfócitos B/metabolismo , Criança , Avaliação de Medicamentos , Monitoramento de Medicamentos/métodos , Humanos , Rituximab , Resultado do TratamentoRESUMO
OBJECTIVES: To assess natural killer (NK) and cytotoxic functions in patients with systemic-onset juvenile rheumatoid arthrithis (soJRA) complicated by macrophage activation syndrome (MAS). METHODS: NK cells (CD56+/TCRalphabeta-), NK T cells (CD56+/TCRalphabeta+) and CD8+ cells were assessed for perforin expression by flow cytometry. NK cytotoxic activity was measured after coincubation of mononuclear cells with an NK-sensitive K562 cell line. RESULTS: Two major patterns of immunologic abnormalities were detected. Four of 7 patients had decreased NK activity, low NK cell numbers, and mildly increased levels of perforin expression in CD8+ and CD56+ cytotoxic cells. Three remaining patients with MAS, however, had decreased NK activity associated with low levels of perforin expression in all cytotoxic cell populations, a pattern indistinguishable from that in carriers of perforin-deficient familial hemophagocytic lymphohistiocytosis. Remarkably, two of these patients had previous episodes of MAS. CONCLUSIONS: NK dysfunction is an immunologic abnormality common to both familial hemophagocytic lymphohistiocytosis and MAS of soJRA. The extent of NK cell abnormalities in soJRA needs to be further investigated.