Self-activation of PMNs in Systemic Onset JIA

Objective The diagnosis and treatment of systemic onset JIA (juvenile idiopathic arthritis) are problematic in clinic since its etiology is still unclear .Some studies suggest that PMNs (Polymorphonuclear Neutrophils) take an important role in the occurrence and development of JIA. To investigate the association between the function of PMNs and the clinical features of JIA and other rheumatic diseases,the proportions of self-activated PMNs in these diseases were evaluated and compared.Methods According to the criteria set in 2001 in Canada,18 patients with systemic JIA were enrolled in the study.Meanwhile,15 patients with oligoarticular JIA,10 patients with KD (Kawasaki Disease),9 patients with SLE (systemic lupus erythematosus) and 27 healthy children with similar age were enrolled as negative controls. To evaluate the levels of self-acitvated PMNs in the patients,four scrutiny points were taken according to the developments of the diseases. The first scrutiny point was from 1 to 5 days after when the patients were admitted the hospital; the second scrutiny point was from 8 to 17 days after the first scrutiny when the symptoms of the patients were relieved; and the third and forth scrutiny points were from 28 to 42 days and from 53 to 70 days after the first scrutiny points,respectively. All the patients were followed up for at least 1 year so that the diagnoses were confirmed. To evaluate the levels of self-activation,DHR (dihydrorhodamine) assay was taken in the four scrutiny points. For each patient,0.5 mL of Heparin anticoagulated venous blood was collected. 50 μL of blood was incubated in PBS (phosphate buffer solution) and PMA (phorbol myristate acetate) respectively for 15 minutes at 37℃ and then incubated with 25 μL of DHR for 5 minutes at 37℃. After that erythrocytes were removed by adding 2 mL of hemolysis and cells were washed once using PBS. Cells were resuspended in 500 μL of PBS and then tested by Flow cytometry. CRP (C reactive protein) and ESR (erythrocyte sedimentation rate) of each patient in routine.Results At the first scrutiny point,the average proportion of self-activated PMNs in systemic JIA patients was (33.94±24.95)% while the average MFI (mean fluorescent intensity) was 10.68±5.03 and they were significantly higher than the negative controls [the proportion of self-activated PMNs and MFI were (8.02±8.11)% and 3.18±1.05,respectively,P0.01)]. The proportion of self-acitivated PMNs and MFI of other rheumatic patients were: oligo-JIA [(5.58±2.77)%,3.38±0.69]; KD[(10.65±6.65)%,4.19±1.14]and SLE [(7.29±2.97)%,3.73±0.87 ]and they were all at the same level of negative controls. At the second scrutiny point,the CRP and ESR levels declined to (34.50±33.65) mg·L~ -1 and (49.56±31.43) mm·h~ -1 ,respeceively(P0.01). The proportion of self-activated PMNs did not decline sighificantly. At the third scrutiny point,the proportion of self-activated PMNs and MFI declined significantly to (7.00±2.96)% and 4.32±1.31,respectively (P0.01). Conclusions PMNs were significantly self-activated in systemic onset JIA patients which suggested that PMNs took an essential role in the pathology of systemic onset JIA while oligo-JIA and other rheumatic disease had no sign of PMNs self-activation.As the relief of clinical symptoms,the proportion of self-activated PMNs decreased significantly which confirmed the role of PMNs in systemic onset JIA. DHR assay could be a valuable test in the diagnosis of systemic JIA and could also be a useful test to evaluate the activity of systemic JIA.

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