Objectives Interferon-γ (IFNγ) is the pivotal mediator in murine models of primary haemophagocytic lymphohistiocytosis (pHLH). Given the similarities between primary and secondary HLH (sec-HLH), including macrophage activation syndrome (MAS), we investigate the involvement of the IFNγ pathway in MAS by evaluating levels of IFNγ and of the induced chemokines, and their relation with laboratory parameters of MAS in systemic juvenile idiopathic arthritis (sJIA) patients with MAS and in a murine MAS model.
Methods The Luminex multiplexing assay was used to assess serum levels of interleukin (IL)-1β, IL-6, IFNγ and of the IFNγ-induced chemokines CXCL9, CXCL10 and CXCL11 in patients with sec-HLH (n=11) and in patients with sJIA (n=54), of whom 20 had active MAS at sampling. Expression of IFNγ-induced chemokines was assessed in IL-6 transgenic mice in which MAS is induced by TLR4 stimulation with lipopolysaccharide.
Results Levels of IFNγ and of IFNγ-induced chemokines were markedly elevated during active MAS and sec-HLH and were significantly higher in patients with MAS compared with active sJIA without MAS. Levels in patients with active sJIA without MAS were comparable to those of patients with clinically inactive sJIA. During MAS, ferritin and alanine transferase levels and neutrophil and platelet counts were significantly correlated with serum levels of IFNγ and CXCL9. In murine MAS, serum levels of ferritin were significantly correlated with mRNA levels of Cxcl9 in liver and spleen.
Conclusions The high levels of IFNγ and of IFNγ-induced chemokines and their correlation with the severity of laboratory abnormalities of MAS suggest a pivotal role of IFNγ in MAS.
- Juvenile Idiopathic Arthritis
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Handling editor Tore K Kvien
Contributors CB, CdM, GP, FDB: study hypothesis and design, writing and reviewing manuscript; CB GS, AAG, SG, AR: samples and clinical and laboratory data from patients. CB, KdG, DPM: correlations and statistical analysis. FG and WF performed the multiplex assays. GP and IC: animal experiments. All the authors reviewed, commented, and approved the final manuscript.
Funding AAG is supported by NIH grants R01-AR059049, and P01-AR048929; GS is supported by a Scientist Development Award from the Rheumatology Research Foundation; GP is supported by the Italian Ministry of Health (Rome, Italy) Young Investigator Grants ‘GR-2011-02347874’. This study was realised in the context of an EU-funded FP7 project, named FIGHT-HLH (306124) coordinated by CDM.
Competing interests KdG, FG, WF, CDM: Novimmune; AAG: Novimmune, Novartis Pharmaceutical Corporation, Roche Pharmaceuticals; FDB: Novartis, Novimmune, Hoffmann-La Roche, SOBI, AbbVie.
Parental/guardian consent Obtained.
Ethics approval Ospedale Bambino Gesu’ Ethical Committee, Istituto Giannina Gaslini Ethical Committee, Cincinnati Children's Hospital Ethical Committee.
Provenance and peer review Not commissioned; externally peer reviewed.