Table 3.

Important cytokines as biomarkers for the diagnosis, activity, and prognosis of sJIA and MAS.

Reference/Year	Cytokines as Biomarkers	Predictive Effects in sJIA and MAS
[9]. Ter Haar, N.M.; Van Dijkhuizen, E.H.P.; Swart, J.F.; Van Royen-Kerkhof, A.; El Idrissi, A.; Leek, A.P.; De Jager, W.; De Groot, M.C.H.; Haitjema, S.; Holzinger, D.; et al. Treatment to Target Using Recombinant Interleukin-1 Receptor Antagonist as First-Line Monotherapy in New-Onset Systemic Juvenile Idiopathic Arthritis: Results From a Five-Year Follow-Up Study. Arthritis Rheumatol. 2019, 71, 1163–1173. https://doi.org/10.1002/art.40865	IL-1	Treat-to-target management with rIL-1Ra as a first-line, short-term monotherapy may be a valuable option to interrupt the pathogenic cycle of sJIA, in which IL-1 is the cornerstone.
[80]. Saccomanno, B.; Tibaldi, J.; Minoia, F.; Bagnasco, F.; Pistorio, A.; Guariento, A.; Caorsi, R.; Consolaro, A.; Gattorno, M.; Ravelli, A. Predictors of Effectiveness of Anakinra in Systemic Juvenile Idiopathic Arthritis. J. Rheumatol. 2019, 46, 416–421. https://doi.org/10.3899/jrheum.180331		Univariate and multivariable statistical analyses of 62 patients diagnosed with sJIA, performed over a period of 14 years to measure the response to treatment with an IL-1 inhibitor (anakinra), identified the clinical profile of patients who can respond successfully to this therapy. Future in-depth studies are needed to detect the biomarkers that could accurately predict response to IL-1 or IL-6 antagonists.
[81]. Lainka, E.; Baehr, M.; Raszka, B.; Haas, J.P.; Hügle, B.; Fischer, N.; Foell, D.; Hinze, C.; Weissbarth-Riedel, E.; Kallinich, T.; et al. Experiences with IL-1 blockade in systemic juvenile idiopathic arthritis—Data from the German AID-registry. Pediatr. Rheumatol. Online J. 2021, 19, 38. https://doi.org/10.1186/s12969-021-00510-8		New strategies in the management of sJIA using IL-1 inhibitors—anakinra and canakinumab—were investigated in a cohort of patients, and the results demonstrated decreased disease activity, inflammatory parameters, and clinical symptoms.
[92]. Brunner, H.I.; Quartier, P.; Alexeeva, E.; Constantin, T.; Kone-Paut, I.; Marzan, K.; Schneider, R.; Wulffraat, N.M.; Chasnyk, V.; Tirosh, I.; et al. Efficacy and Safety of Canakinumab in Patients With Systemic Juvenile Idiopathic Arthritis With and Without Fever at Baseline: Results From an Open-Label, Active-Treatment Extension Study. Arthritis Rheumatol. 2020, 72, 2147–2158. https://doi.org/10.1002/art.41436	IL-1β	IL-1β, as part of the IL-1 family, plays a major role in autoinflammatory diseases, including sJIA. Inhibition of IL-1β rapidly blocks inflammation. Associated with systemic symptoms, IL-1β plays an important role in the pathogenesis of sJIA and the perpetuation of chronic inflammation. Canakinumab, as a monoclonal antibody that inhibits IL-1β and can decrease the levels of IL-6 and the hepatic synthesis of CRP and Fg, rapidly and persistently improved the clinical condition of patients with active sJIA, regardless of whether or not they had fever at the initiation of therapy.
[93]. Kostik, M.M.; Isupova, E.A.; Belozerov, K.; Likhacheva, T.S.; Suspitsin, E.N.; Raupov, R.; Masalova, V.V.; Chikova, I.A.; Dubko, M.F.; Kalashnikova, O.V.; et al. Standard and increased canakinumab dosing to quiet macrophage activation syndrome in children with systemic juvenile idiopathic arthritis. Front. Pediatr. 2022, 10, 894846. https://doi.org/10.3389/fped.2022.894846		An IL-1β monoclonal antibody (canakinumab), given at the onset of MAS-sJIA or even when MAS had developed during treatment with it, can be increased to 2–3 times the normal dose—albeit only in the short term—without any observed secondary effects, attesting to its efficacy in MAS-sJIA, but calling for further studies.
[95]. de Benedetti, F.; Massa, M.; Robbioni, P.; Ravelli, A.; Burgio, G.R.; Martini, A. Correlation of serum interleukin-6 levels with joint involvement and thrombocytosis in systemic juvenile rheumatoid arthritis. Arthritis Rheum. 1991, 34, 1158–1163. https://doi.org/10.1002/art.1780340912	IL-6	High serum IL-6 levels were correlated with the extent and severity of joint involvement, and these data suggest that this cytokine plays a significant role in the pathogenesis of sJIA.
[98]. Brachat, A.H.; Grom, A.A.; Wulffraat, N.; Brunner, H.I.; Quartier, P.; Brik, R.; McCann, L.; Ozdogan, H.; Rutkowska-Sak, L.; Schneider, R. et al. Pediatric Rheumatology International Trials Organization (PRINTO) and the Pediatric Rheumatology Collaborative Study Group (PRCSG). Early changes in gene expression and inflammatory proteins in systemic juvenile idiopathic arthritis patients on canakinumab therapy. Arthritis Res. Ther. 2017, 19, 13. https://doi.org/10.1186/s13075-016-1212-x		Analysis of IL-1β, IL-1 (IL1-R1 and IL1-R2), IL-1 receptor accessory protein (IL1-RAP), and IL-6 expression profiles in patients with sJIA after initiation of treatment with canakinumab found that the best clinical response was in patients with higher initial expression of disordered genes and a strong transcriptional response on day 3. Treatment interrupted a positive feedback loop between IL-1β signaling and IL-1β production. Canakinumab applied in sJIA patients resulted in downregulation of innate immune response genes and decreased IL-6 and clinical symptoms.
[103]. Shimizu, M.; Mizuta, M.; Okamoto, N.; Yasumi, T.; Iwata, N.; Umebayashi, H.; Okura, Y.; Kinjo, N.; Kubota, T.; Nakagishi, Y.; et al. Tocilizumab modifies clinical and laboratory features of macrophage activation syndrome complicating systemic juvenile idiopathic arthritis. Pediatr. Rheumatol. 2020, 18, 2. https://doi.org/10.1186/s12969-020-0399-1		TCZ, a humanized anti-IL-6 receptor monoclonal antibody, could modify the clinical and laboratory features of sJIA-MAS.
[104]. Qu, H.; Sundberg, E.; Aulin, C.; Neog, M.; Palmblad, K.; Horne, A.C.; Granath, F.; Ek, A.; Melén, E.; Olsson, M.; Harris, H.E. Immunoprofiling of active and inactive systemic juvenile idiopathic arthritis reveals distinct biomarkers: a single-center study. Pediatr. Rheumatol. 2021, 19, 173. https://doi.org/10.1186/s12969-021-00660-9		The biomarkers IL-6, IL-18, and S100A12 were confirmed to be increased during active sJIA as compared to healthy controls, and IL-18 was the only one with elevated levels in inactive sJIA. HMGB1 was found to be higher in active than in inactive sJIA. CASP8, CCL23, CD6, CXCL1, CXCL11, CXCL5, EIF4EBP1, KITLG, MMP1, OSM, SIRT2, SULT1A1, and TNFSF11 were found to be differentially expressed in active and/or inactive sJIA compared to the control group.
[107]. Imbrechts, M.; Avau, A.; Vandenhaute, J.; Malengier-Devlies, B.; Put, K.; Mitera, T.; Berghmans, N.; Burton, O.; Junius, S.; Liston, A. et al. Insufficient IL-10 Production as a Mechanism Underlying the Pathogenesis of Systemic Juvenile Idiopathic Arthritis. J. Immunol. 2018, 201, 2654–2663. https://doi.org/10.4049/jimmunol.1800468	IL-10	IL-10 was shown to be an immunosuppressive interleukin that counteracts IFN-γ activity, and disruption of normal IL-10 concentration led to the overproduction of IFN-γ, which participates in the pathogenesis of MAS. This study indicates that defective IL-10 production contributes to the pathogenesis of sJIA.
[108]. Peng, Y.; Liu, X.; Duan, Z.; Duan, J.; Zhou, Y. The Association of Serum IL-10 Levels with the Disease Activity in Systemic-Onset Juvenile Idiopathic Arthritis Patients. Mediators Inflamm. 2021, 2021, 6650928. https://doi.org/10.1155/2021/6650928		Patients with sJIA had higher serum concentrations of IL-10 compared to patients with other febrile illnesses. Serum IL-10 levels were much higher in active sJIA compared with inactive disease and were consistent with ESR, CRP, ferritin, and IL-6 levels. Serum IL-10 could be a valuable marker of sJIA activity.
[110]. Lotito, A.P.; Campa, A.; Silva, C.A.; Kiss, M.H.; Mello, S.B. Interleukin 18 as a marker of disease activity and severity in patients with juvenile idiopathic arthritis. J. Rheumatol. 2007, 34, 823–830.	IL-18	The levels of IL-18 and IL-6 in SF and serum were much higher in patients with sJIA than in other types of disease. The authors concluded that IL-18 is involved in the pathophysiology of JIA, reflects the severity of the disease, and could be a target for the treatment of arthritis.
[111]. Shimizu, M.; Yokoyama, T.; Yamada, K.; Kaneda, H.; Wada, H.; Wada, T.; Toma, T.; Ohta, K.; Kasahara, Y.; Yachie, A. Distinct cytokine profiles of systemic-onset juvenile idiopathic arthritis-associated macrophage activation syndrome with particular emphasis on the role of interleukin-18 in its pathogenesis. Rheumatology 2010, 49, 1645–1653. https://doi.org/10.1093/rheumatology/keq133		The serum level of IL-18 can be considered a biomarker of sJIA activity, and monitoring its profile could be beneficial for distinguishing MAS/HLH and estimating sJIA disease activity.
[112]. Shimizu, M.; Nakagishi, Y.; Inoue, N.; Mizuta, M.; Ko, G.; Saikawa, Y.; Kubota, T.; Yamasaki, Y.; Takei, S; Yachie, A. Interleukin-18 for predicting the development of macrophage activation syndrome in systemic juvenile idiopathic arthritis. Clin. Immunol. 2015, 160, 277–281. https://doi.org/10.1016/j.clim.2015.06.005		IL-18 could be involved in the pathophysiology of MAS, and serum concentrations > 47,750 pg/mL (cutoff value) could be useful in predicting the initiation of MAS.
[113]. Xia, Y.; Cui, P.; Li, Q.; Liang, F.; Li, C.; Yang, J. Extremely elevated IL-18 levels may help distinguish systemic-onset juvenile idiopathic arthritis from other febrile diseases. Braz. J. Med. Biol. Res. 2017, 50, e5958. https://doi.org/10.1590/1414-431X20165958		The levels of IL-18 in patients with sJIA were significantly higher than in other groups of febrile diseases. Serum IL-18 can be used as a biomarker to differentiate sJIA from other febrile diseases.
[115]. Kudela, H.; Drynda, S.; Lux, A.; Horneff, G.; Kekow, J. Comparative study of Interleukin-18 (IL-18) serum levels in adult-onset Still’s disease (AOSD) and systemic onset juvenile idiopathic arthritis (sJIA) and its use as a biomarker for diagnosis and evaluation of disease activity. BMC Rheumatol. 2019, 3, 4. https://doi.org/10.1186/s41927-019-0053-z		The results support the use of IL-18 as an important biomarker in AOSD and sJIA for disease activity.
[116]. Yasin, S.; Fall, N.; Brown, R.A.; Henderlight, M.; Canna, S.W.; Girard-Guyonvarc’hc, C; Gabay, C.; Grom, A.A.; Schulert, G.S. IL-18 as a biomarker linking systemic juvenile idiopathic arthritis and macrophage activation syndrome. Rheumatology 2020, 59, 361–366. https://doi.org/10.1093/rheumatology/kez282		Total IL-18 levels were significantly higher in patients with active sJIA and remained persistently elevated in the majority of those with inactive disease, where IL-18 could predict disease activity and history of MAS, respectively. In active disease, there was a moderate correlation between IL-18 and CXCL9, and a stronger correlation with serum ferritin.
[118]. Mizuta, M.; Shimizu, M.; Inoue, N.; Ikawa, Y.; Nakagishi, Y.; Yasuoka, R.; Iwata, N.; Yachie, A. Clinical significance of interleukin-18 for the diagnosis and prediction of disease course in systemic juvenile idiopathic arthritis. Rheumatology 2021, 60, 2421–2426. https://doi.org/10.1093/rheumatology/keaa634		IL-18 > 4800 pg/mL may be useful for the differentiation between sJIA and other diseases. Monitoring of serum IL-18 concentrations may be useful in predicting disease progression and assessing remission in sJIA.
[128]. Put, K.; Avau, A.; Brisse, E.; Mitera, T.; Put, S.; Proost, P.; Bader-Meunier, B.; Westhovens, R.; Van den Eynde, B.J.; Orabona, C.; et al. Cytokines in systemic juvenile idiopathic arthritis and haemophagocytic lymphohistiocytosis: tipping the balance between interleukin-18 and interferon-γ. Rheumatology 2015, 54, 1507–1517. https://doi.org/10.1093/rheumatology/keu524	INF-γ	Patients with active sJIA and HLH/MAS showed distinct cytokine profiles, with highly elevated plasma levels of IFN-γ and IFN-γ-induced proteins typically found in HLH/MAS. 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.
[129]. Bracaglia, C.; de Graaf, K.; Pires Marafon, D.; Guilhot, F.; Ferlin, W.; Prencipe, G.; Caiello, I.; Davì.; S, Schulert, G.; Ravelli, A.; et al. Elevated circulating levels of interferon-γ and interferon-γ-induced chemokines characterise patients with macrophage activation syndrome complicating systemic juvenile idiopathic arthritis. Ann. Rheum. Dis. 2017, 76, 166–172. https://doi.org/10.1136/annrheumdis-2015-209020		Elevated levels of IFN-γ and IFN-γ-induced chemokines, in combination with other severely altered laboratory parameters in active MAS, support the significant involvement of IFN-γ in MAS.
[130]. Bracaglia, C.; Pires Marafon, D.; Caiello, I.; de Graaf, K.; Ballabio, M.; Ferlin, W.; Davì, S.; Schulert G.; Ravelli, A.; Grom, A.A.; et al. Biomarkers for the Diagnosis and the Identification of Risk of Macrophage Activation Syndrome (MAS) in Systemic Juvenile Idiopathic Arthritis (sJIA) [abstract]. Arthritis Rheumatol. 2017, 69. Available online: https://acrabstracts.org/abstract/biomarkers-for-the-diagnosis-and-the-identification-of-risk-of-macrophage-activation-syndrome-mas-in-systemic-juvenile-idiopathic-arthritis-sjia/ (accessed on 21 August 2022).		IFN-γ and IFN-γ-induced chemokines were significantly increased in active MAS and sec-HLH compared to active sJIA without MAS. In patients with active MAS, serum ferritin, alanine transferase, and neutrophil and platelet counts were significantly correlated with serum IFN-γ and CXCL9 levels. Significant involvement of IFN-γ in triggering MAS was observed.
[67]. De Matteis, A.; Pires Marafon, D.; Caiello, I.; Pardeo, M.; Marucci, G.; Sacco, E.; Prencipe, G.; De Benedetti, F.; Bracaglia, C. Traditional Laboratory Parameters and New Biomarkers in Macrophage Activation Syndrome and Secondary Hemophagocytic Lymphohistiocytosis [abstract]. Arthritis Rheumatol. 2020, 72 (Suppl. S4). Available online: https://acrabstracts.org/abstract/traditional-laboratory-parameters-and-new-biomarkers-in-macrophage-activation-syndrome-and-secondary-hemophagocytic-lymphohistiocytosis/ (accessed on 21 August 2022).		Increased levels of IFN-γ-related biomarkers in patients with MAS and sec-HLH, together with platelet counts and ferritin levels, could be useful for diagnosis, clinical follow-up, and response to therapy.
[131]. Guo, L.; Xu, Y.; Qian, X.; Zou, L.; Zheng, R.; Teng, L.; Zheng, Q.; Leung Jung, L.K.; Lu, M. Sudden Hypotension and Increased Serum Interferon-γ and Interleukin-10 Predict Early Macrophage Activation Syndrome in Patients with Systemic Juvenile Idiopathic Arthritis. J. Pediatr. 2021, 235, 203–211.e3. https://doi.org/10.1016/j.jpeds.2021.02.008		Sudden onset of arterial hypotension, elevated ferritin/ESR ratio, and significantly high levels of IFN-γ and IL-10 are important markers for the early diagnosis of sJIA-MAS.
[135]. Hügle, B.; Hinze, C.; Lainka, E.; Fischer, N.; Haas, J.P. Development of positive antinuclear antibodies and rheumatoid factor in systemic juvenile idiopathic arthritis points toward an autoimmune phenotype later in the disease course. Pediatr. Rheumatol. Online J. 2014, 12, 28. https://doi.org/10.1186/1546-0096-12-28	TNF-α	Many patients developed positive ANA or positive RF, independent of the treatment with anti-TNF drugs, suggesting an autoimmune phenotype rather than an autoinflammatory one in the course of sJIA, probably involving the activation of B cells during the inflammatory process.
[136]. Shimizu, M.; Inoue, N.; Mizuta, M.; Nakagishi, Y.; Yachie, A. Characteristic elevation of soluble TNF receptor II:I ratio in macrophage activation syndrome with systemic juvenile idiopathic arthritis. Clin. Exp. Immunol. 2018, 191, 349–355. https://doi.org/10.1111/cei.13026		sTNFR-II/I had significantly higher levels in patients with sJIA-MAS. Serum IL-18 levels were elevated significantly in MAS patients. Higher serum IL-18 and sTNFR-II/I could be used as biomarkers for the diagnosis of sJIA-MAS, as well as for the differentiation between MAS and EBV-HLH.
[137]. Irabu, H.; Shimizu, M.; Kaneko, S.; et al. Comparison of serum biomarkers for the diagnosis of macrophage activation syndrome complicating systemic juvenile idiopathic arthritis during tocilizumab therapy. Pediatr. Res. 2020, 88, 934–939. https://doi.org/10.1038/s41390-020-0843-4		Serum sTNFR-II/I ratio could be a useful biomarker for assessing disease activity in sJIA-MAS, but also a predictive biomarker for the onset of MAS in the active phase of sJIA, even in patients under TCZ therapy.
[138]. Mizuta, M.; Shimizu, M.; Irabu, H.; Usami, M.; Inoue, N.; Nakagishi, Y.; Wada, T.; Yachie, A. Comparison of serum cytokine profiles in macrophage activation syndrome complicating different background rheumatic diseases in children. Rheumatology 2021, 60, 231–238. https://doi.org/10.1093/rheumatology/keaa299		Serum levels of sTNFR-I for SLE, IL-18 for JDM, and sTNFR-II for KD and sJIA could be useful diagnostic biomarkers for the transition from the active phase to MAS. Overproduction of IFN-γ, IL-18, and TNF-α might be closely related to the onset of MAS.