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OBJECTIVES: To study the role of IFN-γ in the pathogenesis of systemic JIA (sJIA) and haemophagocytic lymphohistiocytosis (HLH) by searching for an IFN-γ profile, and to assess its relationship with other cytokines. METHODS: Patients with inactive (n = 10) and active sJIA (n = 10), HLH [n = 5; of which 3 had sJIA-associated macrophage activation syndrome (MAS)] and healthy controls (n = 16) were enrolled in the study. Cytokines and IFN-γ-induced genes and proteins were determined in plasma, in patient peripheral blood mononuclear cells (PBMCs) and in lymph node biopsies of one patient during both sJIA and MAS episodes. IFN-γ responses were investigated in healthy donor PBMCs, primary fibroblasts and endothelial cells. RESULTS: Plasma IFN-γ, IL-6 and IL-18 were elevated in active sJIA and HLH. Levels of IFN-γ and IFN-γ-induced proteins (IP-10/CXCL-10, IL-18BP and indoleamine 2,3-dioxygenase) in HLH were much higher than levels in active sJIA. Free IL-18 and ratios of IL-18/IFN-γ were higher in active sJIA compared with HLH. HLH PBMCs showed hyporesponsiveness to IFN-γ in vitro when compared with control and sJIA PBMCs. Endothelial cells and fibroblasts expressed IFN-γ-induced proteins in situ in lymph node staining of a MAS patient and in vitro upon stimulation with IFN-γ. CONCLUSION: Patients with active sJIA and HLH/MAS show distinct cytokine profiles, with highly elevated plasma levels of IFN-γ and IFN-γ-induced proteins typically found in HLH/MAS. In addition to PBMCs, histiocytes, endothelial cells and fibroblasts may contribute to an IFN-γ profile in plasma. Increasing levels of IFN-γ compared with IL-18 may raise suspicion about the development of MAS in sJIA.

Original publication

DOI

10.1093/rheumatology/keu524

Type

Journal article

Journal

Rheumatology (Oxford)

Publication Date

08/2015

Volume

54

Pages

1507 - 1517

Keywords

IFN-γ, IL-18, cytokine, haemophagocytic lymphohistiocytosis, macrophage activation syndrome, peripheral blood mononuclear cells, plasma, systemic juvenile idiopathic arthritis, Adolescent, Arthritis, Juvenile, Biopsy, Case-Control Studies, Child, Child, Preschool, Cytokines, Diagnosis, Differential, Endothelial Cells, Female, Fibroblasts, Humans, Infant, Interferon-gamma, Interleukin-18, Interleukin-6, Leukocytes, Mononuclear, Lymph Nodes, Lymphohistiocytosis, Hemophagocytic, Macrophage Activation Syndrome, Male, Young Adult